Internal circuit principle of uPC1225H

V: PC1225H is a 12-pin single in-line package. Its characteristics are: (1) The total harmonic distortion is extremely small. When vc=±
36V and the output power is 30W, the distortion at 1kHz is 0.002%, and the signal distortion at 20kHz is only
0-006%. (2) Power bandwidth, when Po=25W, T=0-1%, the power bandwidth is 900kHz (-3dB).
(3) Strong driving ability, in the range of 20Hz ~ 20kHz, when 7rHD=0.05%, the output voltage reaches 23Vo (4) The internal
circuit is composed of a differential input constant current source and a constant current source load, and has excellent symmetry. The circuit works stably and reliably. In
addition, its small noise figure, large dynamic range, and few external components enable it to have extremely
excellent performance in audio amplifier applications. Its performance parameters are shown in Table 2-32.
    plPC1225H is also equipped with a temperature compensation circuit, a working protection circuit and a quiet voice circuit. Pin 3 of the squelch control terminal
is active at high level. When in use, a 100pL/50V electrolytic capacitor can be connected to this pin to +Vc to eliminate the startup impact sound.
    ℃1225H adopts dual power supply operation, the power supply voltage range is ±18~±36V, the limit operating voltage is ±50v, and
the limit operating current is 0.2A. The allowable power consumption is 4.1. A sufficiently large heat sink should be installed when using it.
    Figure 2-120 is a 50w, two-channel high-odor retention power amplifier circuit assembled from *uPC1225H and 2SC2681, 2SA1141 famous brand tube pairs
. As can be seen from the figure, the peripheral structure of this circuit is very simple, and its performance is very good. Among them,
the transistor VTi and RPl and R4 connected between pins 7 and 8 of Hong PC1225H are external bias circuits recommended by the manufacturer, and the transistors connected between pins 6 and 7 are Capacitor
C3 is an external compensation capacitor. Figure 2-121 is the internal circuit schematic diagram of VPC1225H or
    cPC1237H is the safety protection circuit of this machine. It is a multi-functional power amplifier protection integrated circuit. It can
reliably protect the circuit during startup, shutdown, overload and midpoint drift. It has a simple circuit, stable and reliable operation, and
can be matched with all forms of power amplifier circuits to perform effective protection work.