Diamond Differential BTL Power Amplifier Circuit-Power Amplifier

It is a diamond-shaped differential BTL power amplifier circuit composed of all discrete components.
    The input circuit uses a field effect dedicated differential pair transistor 3DJ5HC. It is a symmetrical production of two field effect transistors on a substrate
. It has the characteristics of consistent parameter characteristics and superior temperature drift performance. In addition to input amplification, it also uses the function of its
inverting input terminal to achieve zero level to solve the interface problem of the amplifier feedback input terminal.
    Transistor VT2 is used as the constant current source of the differential input circuit. The operating current of the input stage is determined by VI and R12, Ic2=
6mA.
    VTio ~ VT13 form a diamond-shaped differential voltage amplification and inverting stage, which consists of two NPN tubes and two PNP tubes,
two pairs of complementary amplifier circuits. The diamond differential circuit has four input terminals, which are connected to the output of the differential input stage, and has four
output terminals, which are used to drive the bridge complementary push-pull output circuit . The diamond differential circuit can not only output a large current, but also
has a much higher common-mode rejection capability than a conventional differential circuit. When the circuit inputs a common mode signal, the currents of VT3 and VTs increase, while
the currents of VT4 and VT6 tend to decrease, but the sum of the currents of VT3 and VT4 is only equal to the sum of the currents of VTs and VT6. The two
trends cancel each other out and no common mode signal is output. When a differential signal is input, the currents of VT3 and VB increase.
The current base of VT4 and VT6 is small. The sum of the currents of VT3 and VT4 is always equal to the sum of the currents of VTs and VT6. The voltage at
both ends always remains stable. There is a negative feedback effect between the upper and lower sets of differential circuits. o Diamond differential The amplifier circuit can also
be regarded as a complementary push-pull amplifier, because it is not limited by quiescent current. When a large transient signal is input,
the amplifier enters a Class B operating state, thereby reducing transient distortion ( The power output stage of the TI M)o
    circuit adopts a bridge push-pull output circuit, and the two sets of output circuits adopt fully symmetrical three-level Darlington
circuits. In order to ensure the safety of the output tube during high power output, the final stage adopts the working method of two tubes in parallel, which makes it
have strong anti-overload ability.
    For a general single-ended push-pull output circuit , it is required that the parameters of the output tube must be matched, and the error should be as small as possible
to ensure that the circuit can work symmetrically, and the positive and negative half cycles of the output signal are completely symmetrical. But for bridge push-pull circuits, the selection of output tubes
does not have to be as strict as single-ended push-pull. Because it can be known from the bridge balance principle of the bridge push-pull circuit that as long as
the products of the equivalent parameters of the diagonal transistors are equal, the bridge can be balanced. Therefore, even if the parameters of the selected power tubes are very different, resulting in
serious asymmetry between the two outputs, the synthetic waveform on the load is still symmetrical. Therefore, the bridge power amplifier circuit can not only
improve open-loop distortion, but also cancel distortion.
    The output tubes VTio - VT12VTii - VT13 and VT22 - VT24, VT23 - VTzs adopt a mid-point floating connection method
.