5W 40-500kHz power amplifier

The preamplifier circuit is a three-stage directly coupled transistor amplifier circuit. VT1 is 3DG32G (the first stage),
which constitutes a common emitter circuit. VT2 is the second stage, using 3DG130B to form a common collector circuit. VT3 is the third stage t. It
uses 3DA76 to form a common emitter circuit port resistor R3 and R 1:0 to form a mixed AC and DC parallel current negative feedback to ensure the
stable operation of the amplifier. 6 The third stage amplifies the amplified circuit through the transformer Tl The signal is sent to the input end of the power amplifier circuit.
    The power amplifier circuit adopts a Class A push-pull amplifier circuit and is composed of two deep negative feedback amplifiers that are completely symmetrical up and down. The input
transformer T2 supplies the pre-sent amplified signal to two identical amplification circuits VT4 (VT5), VT6 (VT" and VT8
(VT9) to form a three-level direct coupling circuit of co-generator, co-collector and co-generator. Among them, VT6 (VT7) is the emitter output device, which is mainly
used for impedance matching of front and rear stages. VT8 (VT9) is a power tube and must be installed on a suitable radiator. T3 is a three-coil output variable
device, so that the upper and lower amplifiers can Push-pull operation is absolutely symmetrical and balanced, and at the same time, the output impedance frequency response is
improved. The advantage of using push-pull is that each transistor can operate in harsh conditions and can even enter the
nonlinear region. If When the transmission characteristics and frequency response of the push-pull transistor are exactly the same, the even-order harmonic
distortion will cancel out. Moreover, the Class A push-pull distortion is much smaller than the Class B push-pull distortion. From the electrical schematic diagram, The two amplifiers
serve as backup for each other, that is, when one of the amplifiers stops working due to a fault, the other amplifier can still continue to work, with only a 6dB drop in output level
and no complete interruption of the signal .