Current expanding circuit of power operational amplifier

Abstract

The invention discloses a current expanding circuit of a power operational amplifier. The circuit is provided with a power operational amplifier unit, a bias circuit unit and a current-expanding triode unit. The power operational amplifier unit is respectively connected with the bias circuit unit and the current-expanding triode unit, the current-expanding triode unit is directly driven by the power operational amplifier unit to reduce the number of circuit stages in use, and the static bias current of the current-expanding triode unit is ensured, so that the crossover distortion is overcome;meanwhile, the bias circuit unit can drive a very low emitter bias resistor and can be used for manufacturing a high-frequency high-current power amplifier; the complexity of the circuit is reduced, the zero drift voltage is reduced, the crossover distortion is improved, and the power supply of the power operational amplifier is stable.

Description

technical field [0001] The invention relates to the field of electrical technology, in particular to a current expansion circuit of a power operational amplifier. Background technique [0002] A power amplifier is an amplifier that can generate the maximum power output to drive a load (such as a speaker) under a given distortion rate. The use of analog power amplifiers for analog signal amplification can be divided into Class A, Class B and Class AB amplifiers. Class D amplifier is a kind of pulse signal that converts the input analog audio signal into PWM (pulse width modulation), and then uses the pulse signal to control the on / off of high-power switching devices, also known as switching amplifier, which has the outstanding advantage of high efficiency. [0003] Power amplifiers are required in many industrial fields. For example, the test of power system traveling wave ranging device requires a power amplifier with a frequency band of 100kHz and a peak current of 60A. T...

AI Technical Summary

Problems solved by technology

[0007] 1. Discrete component scheme: firstly, the circuit of discrete components is complex and difficult to debug, and the long wiring is prone to parasitic oscillation; secondly, the two differential tubes are heated unevenly, resulting in a large voltage drift at the output midpoint

[0008] 2. Multiple power op amps connected in parallel: the output current of the power op amp is still small, and more than 10 parallel connections are required to output 60A. The cost is high; in addition, the amplification factor of the Master op amp and the Slave op amp are different, so the frequency response is also different. There is phase difference and circulating current at high frequency, which affects high frequency characteristics

[0009] 3. Power operational amplifier plus current expansion circuit mode 1: The quiescent current of the power operational amplifier is about 40mA, and the voltage drop of the 1.5Ω resistance is very small, so the bias of the current expansion triode is seriously insufficient, and there is crossover distortion; in addition, the output of the power operational amplifier is large When the current is high, the voltage drop of the 1.5Ω resistor is relatively large, which will cause fluctuations in the power supply of the front-stage circuit of the power operational amplifier, affect its stability and cause interference

[0010] 4. Power operational amplifier plus current expansion circuit mode 2: The bias current of the current expansion transistor is zero, and the 270Ω resistor can only improve the crossover distortion in the low frequency band, and there is still a large crossover distortion in the high frequency band

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