Amplifier that suppresses the influence of power supply waveforms

It is another amplifier that can suppress the influence of power supply fluctuations. In the figure, components such as VT2 and VI)l form a constant current
source, which serves as the load of the voltage amplifier stage rrl. VT3 forms an emitter follower, which is used to reduce the output impedance of the voltage amplifier. This type of amplifier
uses a constant current source as a load. With high gain Kv (about 55dB), the output of VT3 can directly drive the OTL power output stage composed of VT4 ~ VT7. When an 8mV signal is input, the output power can reach 2W. This circuit has a 30dB ability to suppress power supply voltage fluctuations. Therefore, a very simple power supply can be used. As shown in the figure, the power supply filter capacitor only uses 220t.JcFo. This circuit mainly relies on the constant current characteristics of VTz to suppress the influence of power supply fluctuations. The constant current performance of the constant current tube VTz in the circuit is better. The better, the stronger the ability to suppress power supply voltage fluctuations. In addition, the suppression capability can be improved by stringing the negative feedback resistor RE (shown by the dotted line) at the emitter of 'VTz , or increasing the value of VTi. Adjusting Ri or RE in the diagram can change the constant current value, that is, change the static operating point current of VTi. Adjusting R3 can adjust the DC voltage at the output terminal (VTs emitter) so that it is equal to half of the power supply voltage.