ce amplifier lab3a
Figure 1. CE amplifier

Algebra is worse if you avoid it

1. CE amplifier _pnp)

  • Find the small-signal equivalent circuit of this amplifier. Keep all reactive components in the circuit.
    TIP: Split Rx into two resistors R1 and R2 for analysis. The potentiometer and R1/2 ratio is set such that Vout is midway between the transistor’s cutoff and saturation points.

  • What is V(out) when Q1 is in cutoff mode?

  • What is V(out) when Q1 enters saturation mode?

Details

In saturation mode, the transistor is fully switched on and has \(V_{EC}\approx 0\,\mathrm{V}\). Use this effect to morph the circuit into a series of R4, R6, and R5 and find the voltage at the top of R5.

\(V(\mathit{out}) = 10 \dfrac{R_5}{R_4 + R_6 + R_5} - 5 = \)

  • Find the small-signal transfer function \(v_{\mathit{out}} / v_{\mathit{in}}\), including the reactances.

2. HF-1 mic amplifier

ce hf1 micamp
Figure 2. CircuitLab version of the HF-1 mic amp

Draw the small-signal equivalent circuit of Figure 2.

Then compute the voltage gain vout / vs under the assumption that all capacitors are significant.

pm1000 eq2
Figure 3. PM1000 equalizer, bass only

3. Yamaha PM-1000 equalizer

Draw the small-signal equivalent circuit of Figure 3.

Then compute the voltage gain vout / vs under the assumption that all capacitors are significant.