Triode preamplifier ----- Transistor Preamplifier

Triode Preamplifier, Transistor Preamplifier Keywords: front amplifier circuit diagram Even a small and unique full patch component board, which is analyzed as a mono preamplifier. The maximum highlight is that the output of the emitter output is low, and the single-ended push circuit is used in the output terminal is difficult to do in general the output circuit. Circuit Analysis See Figure: The output is composed of V1, V2 two-stage emitter output circuit. The entire circuit impedance is determined in the parallel value of the deflective resistance R1 and the V1 luminance impedance. The loser impedance of V1 is similar to the β1 × RL1, and β1 is the current amplification factor of V1, and RL1 is an equivalent load of V1. Obviously, it is also an emitter outputter, but the function of V2 is to allow V1 to have a higher load impedance, so that the entire circuit has a higher input impedance. In order to ensure that the operating points of V1 and V2 are stable, the input circuit supplies + 18V voltage after Duo regulatory. In terms of direct flow, R2, R3 is in the emitter circuit of V1. R3, R5 In the emitter circuit of V2, they all have a DC negative feedback, so that the static operating point is more stable. V3 is an intermediate amplifier, forms a single-ended push-pull output circuit with V4 and V5. The collector load of V3 is larger than the value of R10 and R11, mainly increasing the voltage gain of the circuit, and the output impedance of the circuit also increases. V4, V5 is an output stage, in order to make the VCC (24V) DC voltage can be assigned to two tubes, V5 collector potentials should be achieved by adjusting the R8 resistance. In order to cause the output voltage to have a certain amplitude, a shut-off distortion occurs when the large signal is prevented, V4, and the V5 static collector current is 29mA, and the flow pressure drop is 0.2 V on the R16. I use the common components to try with a common component, and the effect can be compared with the classic Malanti PM preamplifier with a common component. Note that the transistor should all adopt high frequency transistors. V1 and V2 should be selected from PNP silicon tubes, V1 β value is 250, and V2 β value is 200. The β value should not be too large, otherwise the circuit stability is poor, such as 9015, etc. The beta value of V3 should take 150, depending on the static working current of 20 mA, the power tube should be selected, such as 3cg120, etc. The β value of V4, V5 should be 100, and the medium power tube should be selected, such as 3DG130, and the like. The regulator tube should use 18V voltage regulated values. Resist, there is no special requirement. Everyone may wish to try! Author: 福 福

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