Simple and concise DC power amplifier

The principle of a pure DC power amplifier composed of B's ​​'' ROHM " series transistors is shown in Figure 6-18 (the power supply and protection circuit are omitted). The performance parameters of part a ROHM tube and the characteristics of this power amplifier are shown in Table 6-2 and Table 6-3 display. The input signal is low-pass processed by C2. Rl and then sent to ICIA for buffer amplification. Then the voltage amplification stage composed of ICIB and VT1 ~ VT4 amplifies the voltage , and then sends the signal to VT6 . The current driving stage composed of VT7 is finally completed by VT8. VT9. The power amplification stage is completed by LC using authentic NE55320 VT1 and VT2, and C556.C546 with T up to 500MHz, which plays a vital role in improving the transient response of the amplifier. VT3 ~VT9 all uses medium and high power tubes from ROHM . In particular, the VT5 medium- power tube series can track the temperature of high-power tubes well and more effectively correct the operating point drift of the power amplifier caused by temperature rise . After the circuit is installed and checked, it can be powered on. Adjust R28 so that the voltage drop across R28 is 5~8mV, and then replace it with a fixed resistor of the same resistance (at this time, the quiescent current of VT8 and VT9 is 20~32mA) .