Diamond differential input power amplifier circuit

Almost all DC power amplifier circuits use differential circuits as the input stage. Many circuits also use complementary symmetrical double differential
circuits and complementary double differential circuits with constant current sources as input stages. Because the constant current source has a high dynamic impedance t and
has a negative feedback effect on the common-mode signal, the circuit has high stability. However, it is precisely because of the limitation of "constant current" that when a
large amplitude transient signal is input, the transient characteristics of the circuit will deteriorate. The diamond differential circuit evolved from the double differential circuit
. It has the advantages of the double differential circuit and overcomes its shortcomings, greatly improving the performance of the circuit. Figure 2-37 is a
DC power amplifier circuit using a diamond differential circuit as the input stage.
    VTi-VT4 forms a diamond differential input stage. (RP. R6) is the collector load of vTI , and R is
the collector Load o R7, center, Rio, and Rl 1 are the emitter resistors of VTi ~ VT4 respectively. On the one hand, they jointly establish
the DC operating point of this stage with the bias circuit, and they are also the current negative feedback resistors of this stage. R2, VDi, R3, R, VI, and R
are the DC bias circuits of VTi.VT3. R12, VI, R13, R14, VI) 4, and Ris constitute the DC
bias circuits of VT2 and VT4.
    The input signal is input to point A via cl. C2, Ri, the input resistor and capacitor form a low-pass filter with a turning frequency of 60kHz
to limit the high-frequency components in the input signal.
    VTs, VT6 and their bias resistors form a complementary push-pull voltage amplification stage. R16 and Rl7 are connected in parallel with the input impedance of the subsequent stage
to form the load of VB and VT6. VT7 and Ri"‰ form an output bias circuit. C4 is The high-frequency bypass
capacitor makes the AC voltage drop Vm approach 00 at higher frequencies.
    The output stage uses a complementary push-pull power output stage composed of three-stage Darlington tubes. VTa, VTio.VT12 form
a Darlington The NPN tube of the Dayton tube, VTg, VTiI, and VT13 form a PNP tube. VT8 and VTg adopt a midpoint floating connection
method, & is their bias resistor and also the feedback resistor.
    From the output midpoint E to the diamond differential The inverting input terminal B of the input stage forms a DC feedback loop. At the same time,
the capacitor C3 is connected to terminal B to make the AC potential at point B zero, thereby cutting off the negative feedback loop of the large AC loop and becoming only
DC negative feedback. DC power amplifier circuit without AC negative feedback .
    This circuit uses separate power supplies for the front and rear stages. The front stage uses a regulated power supply, and the output stage uses a rectified and filtered power
supply, and uses a lower voltage.