Current consumption - 46 mA. The bias voltage V bjas determines the output power level (gain) of the amplifier

Fig. 33.11. Internal structure and pinout of TSH690, TSH691 microcircuits

Rice. 33.12. Typical inclusion TSH690, TSH691 microcircuits as an amplifier in the frequency range 300-7000 MHz

and can be adjusted within 0-5.5 (6.0) V. The transmission coefficient of the TSH690 (TSH691) microcircuit at a bias voltage V bias = 2.7 V and a load resistance of 50 Ohms in a frequency band up to 450 MHz is 23 (43) dB, up to 900(950) MHz - 17(23) dB.

Practical inclusion of TSH690, TSH691 microcircuits is shown in Fig. 33.12. Recommended element values: C1=C5=100-1000 pF; C2=C4=1000 pF; C3=0.01 µF; L1 150 nH; L2 56 nH for frequencies not exceeding 450 MHz and 10 nH for frequencies up to 900 MHz. Resistor R1 can be used to regulate the output power level (can be used for an automatic output power control system).

The broadband INA50311 (Fig. 33.13), manufactured by Hewlett Packard, is intended for use in mobile communications equipment, as well as in consumer electronic equipment, for example, as an antenna amplifier or radio frequency amplifier. The operating range of the amplifier is 50-2500 MHz. Supply voltage - 5 V with current consumption up to 17 mA. Average gain

Rice. 33.13. internal structure microcircuits ΙΝΑ50311

10 dB. The maximum signal power supplied to the input at a frequency of 900 MHz is no more than 10 mW. Noise figure 3.4 dB.

A typical connection of the ΙΝΑ50311 microcircuit when powered by a 78LO05 voltage stabilizer is shown in Fig. 33.14.

Rice. 33.14. broadband amplifier on the INA50311 chip

Shustov M. A., Circuitry. 500 devices on analog chips. - St. Petersburg: Science and Technology, 2013. -352 p.

The high-frequency amplifier offered to the attention of readers can find the most wide application. This is an antenna amplifier for a radio receiver, and an amplification attachment for an oscilloscope with low sensitivity of the vertical deviation channel, and aperiodic amplifier IF, and instrumentation amplifier.

The amplifier's input and output are designed to be connected to a line with a characteristic impedance of 75 Ohms. The operating frequency band of the amplifier is 35 kHz - 150 MHz with unevenness at the edges of the range of 3 dB. Maximum undistorted output voltage 1 V, gain (at 75 Ohm load) - 43 dB, noise figure at 100 MHz - 4.7 dB. The amplifier is powered from a 12.6 V source, current consumption is 40 mA.

Schematic diagram amplifier is shown in the figure. It consists of two series-connected amplification cells, in each of which resistive amplifier stages on transistors N1, T3 are loaded onto emitter followers on transistors T2, T4. To expand the dynamic range, the current through the last emitter follower is selected to be about 20 mA. The amplitude and frequency characteristics of the amplifier are formed by elements of the frequency-dependent feedback circuit R4C2, R10C5 and simple high-frequency correction chokes Dr1 and Dr2.

Structurally, the amplifier is made on a printed circuit board made of foil fiberglass and placed in a silver-plated brass case.

The connectors are high-frequency connectors SR-75-166 F. High-frequency chokes Dr1 and Dr2 are frameless. Their windings contain 10 turns of PEV-1 0.25 wire, the diameter of the windings is 5 mm.

If 43 dB gain is excessive, only one amplification cell can be used, depending on the intended purpose, either on T1 transistors. T2 with a supply voltage of + 5 V, or on transistors T3, T4 with a supply voltage of +12.6 V. In the first case, the noise figure is lower, but the maximum output voltage is also lower (about 400 mV); in the second case, the noise figure is slightly higher, but the maximum voltage across a 75 Ohm load is 1 V. The gain of both amplification cells is approximately the same (21-22 dB) over the entire range of the specified operating frequencies, and when using one cell the frequency band is even wider ( from 30 kHz to 170 MHz with unevenness at the edges of the range of 3 dB).

In conclusion, it should be noted that when assembling the amplifier, strict compliance with the requirements for installation in the decimeter range is mandatory.

Source: Radio 7/76

This diagram is also often viewed:

Power amplifier 10 W

The amplifier is designed to work with a transver having a P output of up to 1 watt. The exciter load, which ensures stable operation on all ranges, is resistor R1. The setting consists of setting the quiescent current VT2 within 0.3 A (in the absence of a signal at the input).

A 1 volt signal at the input increases the output power in the antenna to 10 watts. Reception-transmission switching is carried out from an external control circuit, which is closed to the housing when switching to transmission. In this case, relay K1 is activated and connects the antenna to the output of the power amplifier. When the control circuit breaks, a positive voltage appears at the base of VT1, opening it. Accordingly, the VT1 collector is near zero. Transistor VT2 closes. Relay type RPV2/7 passport RS4.521.952 Chokes L1 and L2 type D1 (1A) with inductance 30 and 10 μH, respectively. Frame diameter L3- 15 mm PEV2 wire 1.5 mm

Wideband power amplifier

Drozdov VV (RA3AO)

To work in conjunction with an all-band HF transceiver, you can use a broadband power amplifier, the circuit diagram of which is shown in Fig. 1. In the ranges of 1.8-21 MHz, its maximum output power in telegraph mode with a power supply voltage of +50 V and a load resistance of 50 Ohms is about 90 W, in the range of 28 MHz - about 80 W. The peak output power in single-sideband amplification mode with an intermodulation distortion level of less than -36 dB is about 80 and 70 W, respectively. With well-selected amplifier transistors, the level of the second harmonic is less than 36 dB, the third harmonic is less than 30 dB in linear amplification mode and less than 20 dB in maximum power mode.

The amplifier is assembled using a push-pull circuit using powerful field-effect transistors VT1, VT2. The long line type transformer T1 provides the transition from an asymmetrical excitation source to the symmetrical input of a push-pull stage. Resistors R3, R4 allow you to match the input impedance of the cascade with a 50-ohm coaxial line with an SWR of no more than 1.5 in the range of 1.8 -30 MHz. Their low resistance provides the amplifier with very good resistance to self-excitation. To set the initial bias corresponding to the operation of the transistors in mode B, use the circuit Rl, R2, R5. Diodes VD1, VD2 and VD3, VD4 together with capacitor C7 form a peak detector of the ALC circuit and protect transistors from overvoltages in the drain circuit. The operating threshold of this circuit is determined mainly by the stabilization voltage of the zener diode VD9 and is close to 98 V. Diodes VD5-VD8 serve for “instant” protection of the drain circuit from overvoltages. The T3 long line type transformer provides the transition from the amplifier's symmetrical output to an unbalanced load. To ease the requirements for the broadband of this transformer and reduce possible voltage surges in the drain circuit, a symmetrical low-pass filter C8L1C10, C9L2C11 with a cutoff frequency of about 30 MHz is connected in front of the transformer.

Installation of a mounted amplifier. The amplifier is assembled on a ribbed heat sink made of duralumin with dimensions of 110x90x45 mm. The fins are milled on both sides of the radiator, their number is 2x13, the thickness of each is 2 mm, the height is 15 mm on the side of the transistor installation and 20 mm on the side of the nuts for their fastening. On the longitudinal axis of the radiator, at a distance of 25 mm from the transverse axis, areas with a diameter of 30 mm are milled for installing transistors, and with reverse side- for fastening nuts. Between the transistors, a “common wire” bus is laid on the radiator fins, cut from sheet copper 0.5 mm thick and attached to the base of the radiator with two M3 screws, passed between the two central ribs at distances of 10 mm from its edges. Tire dimensions - 90x40 mm. Mounting posts are attached to the bus. Coils L1 and L2 are frameless and wound with bare copper wire with a diameter of 1.5 mm on a mandrel with a diameter of 8 mm. With a winding length of 16 mm, they have five turns. Transformer T1 is wound with two twisted wires PEL.SHO 0.31 with a twist pitch of about three twists per centimeter on a ring magnetic core made of M400NN ferrite of standard size K10x6x5 and contains 2x9 turns. Transformers T2 and T3 are wound on ring magnetic cores made of ferrite of the same brand, standard size K32x20x6. Transformer T2 contains 2x5 turns of twisting from PELSHO 0.8 wires with a step of two twists per centimeter, T3 - 2x8 turns of such twisting. Capacitors Cl - C3 - type KM5 or KM6, C4-C7-KM4, C8-C11-KT3.

Setting up a properly assembled amplifier with serviceable parts comes down to adjusting the inductances of coils L1 and L2 for maximum output in the 30 MHz range by compressing or stretching the turns of the coils and setting the initial bias using resistor R1 to minimize intermodulation distortion in single-sideband signal amplification mode.

It should be noted that the level of distortion and harmonics largely depends on the accuracy of the selection of transistors. If it is not possible to select transistors with similar parameters, then for each transistor you should make separate circuits for setting the initial bias, and also, to minimize harmonics, select one of the resistors R3 or R4 by connecting additional ones in parallel with it.

In linear amplification mode in the ranges of 14-28 MHz, thanks to the presence of low-pass filters C8L1C10, C9L2C11, the harmonic level at the amplifier output does not exceed the permissible limit of 50 mW, and it can be connected directly to the antenna. In the ranges of 1.8-10 MHz, the amplifier should be connected to the antenna through a simple low-pass filter, similar to the C8L1C10 circuit, and two filters are sufficient, one for the ranges of 1.8 and 3.5 MHz, the other for the ranges of 7 and 10 MHz. The capacity of both capacitors of the first filter is 2200 pF, the second is 820 pF, the inductance of the coil of the first is about 1.7 μH, the second is about 0.6 μH. It is convenient to make frameless coils from bare copper wire with a diameter of 1.5 - 2 mm, wound on a mandrel with a diameter of 20 mm (the diameter of the coils is about 25 mm). The first filter coil contains 11 turns with a winding length of 30 mm, the second - six turns with a winding length of 25 mm. The filters are adjusted by stretching and compressing the turns of the coils to achieve maximum output in the ranges of 3.5 and 10 MHz. If the amplifier is used in overvoltage mode, separate filters should be turned on on each range.

The amplifier input can also be matched with a 75-ohm coaxial line. To do this, the values ​​of resistors R3, R4 are 39 Ohms. The power consumed from the exciter will decrease by 1.3 times, but the gain cutoff in high-frequency ranges may increase. To equalize the frequency response, coils with an experimentally selected inductance, which should be about 0.1-0.2 μH, can be connected in series with capacitors C1 and C2.

The amplifier can be directly loaded into a resistance of 75 Ohms. Thanks to the action of the ALC loop, the linear undervoltage mode of its operation will remain, but the output power will decrease by 1.5 times.

Power amplifier on KP904

E. Ivanov (RA3PAO)

When repeating the UY5DJ power amplifier (1), it turned out that the most critical component that reduces the reliability of the entire amplifier is the output stage. After experiments on various types bipolar transistors had to switch to field-effect ones.

The output stage of the UT5TA broadband amplifier (2) was taken as the basis. The diagram is shown in Fig. 1. new details are highlighted with thicker lines. A small number of parts made it possible to mount the cascade on a printed circuit board and heatsink from UY5DJ in place of the parts and transistors of the UY5DJ amplifier. The quiescent current of the transistors is 100...200 mA.

Wideband RF Amplifiers

In most cases of amateur radio design, monolithic integrated circuits should be preferred when designing high-frequency devices. However, when high sensitivity and wide dynamic range are needed, the following reactive feedback amplifier circuits may be useful.

Amplifier in Fig. 2.1-1 is intended for use in UHF and IF input stages. It has a wide dynamic range and linear frequency response over a wide frequency range. With some changes in inductances and capacitances, the amplifier is applicable in the range from 1 to 300 MHz.

Scheme in Fig. 2.1-2 is identical to the diagram in Fig. 2.1-1 except that in in this case the amplifier can be directly connected to a balanced load. If an output impedance different from that indicated in the diagram is required, then change the number of turns in the windings (1-2) and (1"-2") of the high-frequency transformer Tr1 (the dependence here is quadratic, for example, when the number of turns in these windings is 5(1-2 )+5(1"-2") we get an output impedance of 50 Ohms. And at 20(1-2)+20(1"-2") - 800 Ohm).

Amplifier in Fig. 2.1-3 is intended for use in stages that require high input impedance. It also provides wide dynamic range and linear frequency response. The amplifier input impedance is more than 1 kOhm. If it is necessary to reduce this value, inductor L1 is replaced with a resistor of the appropriate value or its inductance is changed so that the reactance at the operating frequency is equal to the required input resistance.

All described amplifiers use broadband transformers of identical design. Pay attention to that. that the ferrite core used must be designed for use in the operating frequency range of the amplifier.

The number of turns in transformers is determined both by the type (size and magnetic permeability) of the core and by the frequency range in which the amplifier is expected to be used.

The indicated relationships are also valid for the transformers used in the mixer circuits below. The location and winding density are selected to achieve the best circuit parameters.

In Fig. 2.1-4, for example, shows a diagram of a universal generator using an amplifier according to scheme 2.1-3. Such a generator can be used in radio stations, as a local oscillator in receiving devices or for measurement purposes.

Rice. 2.1-1 Amplifier stage for the input paths of highly sensitive UHF and IF

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Rice. 2.1-2 Amplifier stage with balanced output

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Rice. 2.1-3 High input impedance amplifier stage

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Rice. 2.1-4 Universal RF generator

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F.1 Determination of the number of turns in transformers

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2. Faucets

Faucets

Mixers in fig. 2.1-5 and fig. 2.1-6 operate at frequencies of 1-300 MHz (formulas for calculating inductances, see above). Both schemes introduce an attenuation of 5...6.5 dB, provide a wide bandwidth and are applicable in a wide variety of designs.

Rice. 2.1-5 Simple balanced and ring balanced mixer

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2. Circuits for amplifying and processing low and medium frequency signals.

Circuits for amplifying and processing low and medium frequency signals.

1. Low noise preamplifier with low input impedance.

Low noise preamplifier with low input impedance

Amplifier in Fig. 2.2-1 has an input impedance of 5 Ohms, obtained through the use of PIC and OOS in certain ratios. Part of the emitter signal of transistor VT2, supplied to the base of VT1, creates OOS, and the collector signal VT3 - POS. Thanks to the low input impedance, the noise characteristics of the amplifier are significantly improved. The spectral density of self-noise with the input open is 2*10(-4) µV/Hz. The gain is 40. The bandwidth is determined by capacitance C1.

Rice. 2.2-1 Low noise preamplifier with low input impedance

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2. Low noise preamplifier with high input impedance.

Low noise, high input impedance preamplifier

At the amplifier input in Fig. 2.2-2 a field-effect transistor is used in a circuit with an OP. The second cascade is made on bipolar transistor according to the scheme with OE. The amplifier has two OOS loops. From the collector of transistor VT2 through the chain R6, NW, the feedback signal is supplied to the source of the field-effect transistor, and from the source through capacitor C2 and resistor R3 to the gate VT1. The presence of a second OOS allows you to increase the input impedance of the amplifier to tens of megaohms and reduce the input capacitance.

The gain can be set from 1 to 100, which also changes the bandwidth. For a gain factor of 4, the bandwidth is in the range of 100Hz-40 MHz. Input impedance 30 MΩ, maximum output voltage 1.5 V.

Rice. 2.2-2 Low Noise High Input Impedance Preamplifier

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3. Microphone amplifier.

Microphone amplifier

In Fig. 2.2-3 shows a diagram of a microphone amplifier built into a microphone holder and powered through a two-wire cable. The circuit works with dynamic microphones and is characterized by good noise immunity. The output signal is taken from resistor R4. Bias to the base of transistor VT1 and temperature stabilization of the amplifier are provided by divider R2 and R3. Resistor R1 is the load of the first stage and provides OOS in the second stage. Feedback reduces non-linear distortion and provides an output impedance of 600 ohms. Bandwidth 16-12500 Hz. Gain factor 200.

Rice. 2.2-3 Schematic diagram of a microphone amplifier

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4. Microphone amplifier with correction, combined with a noise suppression circuit for radio stations and intercoms.

Microphone amplifier with correction, combined with noise suppression circuit for radio stations and intercoms

Scheme in Fig. 2.2-4 is built on the basis of the KR1401UD2 microcircuit, which contains four identical op-amps. The first part of the circuit (elements DA1.1. DA 1.2) performs

function of a microphone amplifier with subsequent correction of frequency response, dynamic change in gain depending on the signal level and limitation of the amplitude of the output signal (which is necessary, for example, to limit the modulation depth in radio stations). Second part of the circuit (DA1.3, DA1.4)

carries out noise suppression in the low-frequency signal, which is necessary to prevent the reproduction of a constant background sound in radio stations, intercoms, etc.

The level of operation of the noise reduction system is regulated by resistor R13, the volume of the low-frequency output signal is regulated by resistor R 17. Trimmers R3, R5 are set to the position of best audibility of the useful signal with the greatest attenuation of noise when the noise reduction is turned off. Capacitor C16 is selected to provide the required bandwidth of the microphone amplifier. The value of resistor R24 ​​depends on the design of the sound receiver and the type of microphone used. The same can be said about resistor R22, which regulates the gain of the cascade at op-amp DA1.2.

Rice. 2.2-4 Microphone amplifier circuit with frequency response correction and wide dynamic range, combined with a noise suppression circuit

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5. Pulse noise suppression device.

Impulse suppression device

In Fig. 2.2-5 shows a schematic diagram of a symmetrical limiter that limits short-term impulse noise. Bandwidth up to 100 kHz. With a useful signal frequency of 3 kHz, the level of impulse noise exceeding the signal level by 300-500 times and the noise duration of 20-30 μs, the circuit reduces the noise level by 30-40 dB.

Rice. 2.2-5 Scheme of a device for suppressing impulse noise

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6. Serial signal mixer.

Serial signal mixer

Mixer in fig. 2.2-6 is built on two field-effect transistors. The first transistor is the dynamic load of the second. The heterodyne signal, which is supplied to the gate VT2, is modulated by the converted signal supplied to the gate VT1. For small input signal values, the output signal is linearly dependent on the input signal. When the input signal is more than 1.2V, nonlinear distortion appears. The mixer operates in the audio frequency range. At frequencies above 500 kHz, the interelectrode capacitances of the PT begin to affect, which reduce the transmission coefficient of the mixer.

Rice. 2.2-6 Schematic diagram of a serial signal mixer

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3. Elements of automation devices.

Elements of automation devices.

1. Amplifier for capacitive sensors.

Lambda diode

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Rice. 2.3-3 Lambda diode

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2. Cable amplifier for remote sensor.

Amplifier for capacitive sensors

In Fig. Figure 2.3-1 shows a pre-amplifier circuit for capacitive sensors with low-voltage power supply. Current consumption - 10 mA, input resistance - 1 MOhm, output resistance - 5 kOhm. The cutoff voltage of VT1 should be less than 1 V.

Cable amplifier for remote sensor

To transmit signals from sensors remote from measuring instruments, amplifiers are used, the output signal and supply voltage in which are supplied through one cable. In Fig. Figure 2.3-2 shows a circuit with 100% OOS (Rin = 2*10^3 MOhm, In = 2.5 pF). The transmission coefficient in the frequency range from 10 Hz to 50 MHz lies in the range of 0.9-0.92. Amplifier noise in the frequency band 5 Hz -300 kHz is 10 μV with the input closed. To reduce external interference on the input circuits, careful shielding of the entire amplifier, especially the input circuits and the sensor, is necessary.

Lambda diode

The device in Fig. 2.3-3 consists of two field effect transistors different conductivity. At zero gate voltage, both transistors conduct. In the diagram they are included in the OOS circuit

therefore in relation to one another. The current flowing through transistor VT1 creates a voltage drop across VT2, closing VT1. In turn, the resistance of VT2 changes depending on the voltage drop across VT1. Thus, as the current flow increases, both transistors tend to close. When the voltage drop across the transistors reaches the cutoff level, the current flowing will be close to zero. For the KP103I transistor the cut-off voltage is 4 V, for the KP3O3D transistor the cut-off voltage is 8 V.

Rice. 2.3-1 Amplifier for capacitive sensors

Rice. 2.3-2 Cable amplifier for remote sensor

Rice. 2.3-3 Lambda diode

3. Lambda diode.

Amplifier for capacitive sensors

In Fig. Figure 2.3-1 shows a pre-amplifier circuit for capacitive sensors with low-voltage power supply. Current consumption - 10 mA, input resistance - 1 MOhm, output resistance - 5 kOhm. The cutoff voltage of VT1 should be less than 1 V.

Cable amplifier for remote sensor

To transmit signals from sensors remote from measuring instruments, amplifiers are used, the output signal and supply voltage in which are supplied through one cable. In Fig. Figure 2.3-2 shows a circuit with 100% OOS (Rin = 2*10^3 MOhm, In = 2.5 pF). The transmission coefficient in the frequency range from 10 Hz to 50 MHz lies in the range of 0.9-0.92. Amplifier noise in the frequency band 5 Hz -300 kHz is 10 μV with the input closed. To reduce external interference on the input circuits, careful shielding of the entire amplifier, especially the input circuits and the sensor, is necessary.

Lambda diode

The device in Fig. 2.3-3 consists of two field-effect transistors of different conductivity. At zero gate voltage, both transistors conduct. In the diagram they are included in the OOS circuit

therefore in relation to one another. The current flowing through transistor VT1 creates a voltage drop across VT2, closing VT1. In turn, the resistance of VT2 changes depending on the voltage drop across VT1. Thus, as the current flow increases, both transistors tend to close. When the voltage drop across the transistors reaches the cutoff level, the current flowing will be close to zero. For the KP103I transistor the cut-off voltage is 4 V, for the KP3O3D transistor the cut-off voltage is 8 V.

Rice. 2.3-1 Amplifier for capacitive sensors

Rice. 2.3-2 Cable amplifier for remote sensor

Rice. 2.3-3 Lambda diode

4. Voltage and current converters.

Voltage and current converters.

1. Voltage multipliers.

Voltage multipliers

When designing high voltage circuits great importance The simplicity and quality of operation of the device is influenced by the selected conversion circuit. Below are several voltage multiplier circuits for use in a wide variety of devices.

In Fig. Figure 2.4-1 shows voltage doubler circuits. The capacities in all doublers are chosen to be the same. The operating voltage of the capacitors should exceed that shown in the diagrams with a margin. Diodes must be selected accordingly. The greater the current required in the load, the greater the capacitance the capacitors must have. Naturally, when the voltage increases using diode-capacitive multipliers, the load current decreases proportionally.

Similarly, multiplication by three or more times is performed.

The multiplier circuits shown here can be used in voltage-to-voltage converters. For example, a diagram of the use of a diode multiplier by 2 is shown (Fig. 2.4-5).

The converter (Fig. 2.4-5) consists of a generator assembled on transistors VT1, VT2 and a diode-capacitor multiplier. The generator frequency is determined by C 1 and resistors Rl, R2. The output signal of the generator passes through a multiplying chain and charges capacitor C5. The multiplier is designed for output current up to 10 mA. To increase the load current, it is necessary to install an emitter follower after the generator and increase the capacitance of capacitors C2-C4.

Rice. 2.4-1 Voltage doubler circuits

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Rice. 2.4-2 Schemes for multiplying by three, six and eight

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Rice. 2.4-3 Multiply by four circuit, voltage converter

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2. Voltage-current converter.

Voltage-to-current converter

In the converter circuit in Fig. 2.4-6, the collector current of transistor VT4 is determined by the expression: Ikvt4 = ​​Uin/R1. This current causes a voltage drop at the collector-emitter junction of transistor VT1. Since VT1 and VT2 are of the same type, the voltage on VT2 will be similar, and, accordingly, the current flowing through VT2, VT3 will coincide with the current in VT4. The maximum output current is determined by the permissible power dissipation of transistor VT3. For currents above 5 mA, the nonlinearity of the conversion is no more than 1%. Any K544 series op amp can be used as DA1. K574, enabled by standard scheme.

Current-voltage converter

The converter in Fig. 2.4-7 is built on the principle of amplifying the voltage that occurs when current flows through resistor R6. The circuit provides Uout = K*Iin - Circuit conversion coefficient K = R6*(R3/R4). To configure the op-amp at Iin=0, resistor R2 is used. Part of the input current is branched into the circuit R1, R2, R3. Resistor R6 is wirewound (nichrome).