SU964656A1 - Device for biasing output voltage of operational amplifier - Google Patents

Description

G -. , The invention relates to a measurement technique and can be used to create digital-analog and analog-digital converters. There are known devices for increasing the output power of an operational amplifier (DU) using a power amplifier at additional transistors, and the power stage is included in the negative feedback circuit of the DI 1 . The disadvantages of these devices are cumbersome and expensive due to the large number of elements included in the feedback circuit of an op amp. The device closest to the proposed device is a device for increasing the output voltage of operational amplifiers, containing op amps with two constant amplifiers connected at the output of the op amp. current feedback from their output to the input of the op-amp 2. The disadvantages of the known device are its complexity and the limited range of bias of the output voltage. The purpose of the invention is to expand the range of the output voltage offset and simplify the device. To achieve the goal, the device for biasing the output voltage of the operational amplifier, containing the first and second large-scale resistors, the first terminals of which are connected to the inverter output of the operational amplifier, the non-inverting input of the operational amplifier through the third large-scale resistor connected to the zero potential bus the resistor is the input of the device, contains a stabilizer and an emitter follower, the input of which is connected through the stabilizer to the output of the operational amplifier And an output coupled to a second terminal of the second scaling PE. and is the output of the device. FIG. 1 and FIG. 2 shows the scheme of the proposed device with negative and positive offset, respectively. The output biasing device on the OP0 of the OU 1 with the input scale resistor 2 and the scale resistors 4 consists of a zener diode and a transistor 6. The transistor 6 and the limiting resistors 7 and 8 form an equilibrium repeater 9, feedback from the output of the OU through scale resistor k. The input voltage is applied through a resistor 2. The device's transmission coefficient is determined from the expression where R4 is the resistance of resistor 4, R is the resistance of the resistor 2. To decrease (zero offset from the input current, resistor 3 is turned on and its value is selected Output Limit Voltage O and the output voltage of the device is related by the following relation o, Uebix-U,, i where the output voltage of the operational amplifier; ebtx the output voltage of the device; C ,, - is the voltage drop on the stabilizer of 5; living base-emitter transition transistor 6, its value can be regarded as absolute and equal to 0, 8 V. The limitations imposed by the proposed device on the input and output voltages are determined by the limit values of the output voltages of the op-amp (iJo max) 1 (W. m W n - r - GO 0 max / 1

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Claims (1)

Invention Formula A device for biasing the output voltage of an operational amplifier containing the first and second large-scale resistors, the first terminals of which are connected to the inverting input of the operational amplifier, non-inverting6 4 Vary UQ can be changed in a wide range. A distinctive feature of the proposed displacement device is the half. for independence Ugjj, OT of instability, and, since the magnitude of the output voltage is determined only by the relation. In FIG. 1 shows a circuit for producing output voltages with a negative bias (), FIG. 2 shows a bias circuit for the positive side (). The only difference from the first circuit is that the conductivity of the transistor 6 changes to the opposite, the polarity of switching on the Zener diode 5 and the power sources. The proposed device provides the following advantages over existing devices: Thus, the proposed device allows wide-range bias-output voltages, circumvention of limitations imposed by the operating range Ug (, | TtOy and the value of the common-mode voltage (ratio ( 2) and (G)). The value of Uebi in the proposed device does not depend on the instability of the Zener diode X% t of the voltage across the base and emitter of the output transistor (relation (1)). The proposed device is simpler, cheaper, and consumes less energy and is suitable for obtaining output voltage bias, of any polarity, and the use of an emitter follower as an output element allows an increase in the load current. creating a DAC and ADC.