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Preparation

1.

Choose a value of R_E so that $V_C \approx 4.5$ V, using the minimum value of $\beta$. (use standard resistor values 1, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2, 10 Ohms $\pm10\%$ and decade multiples.)

2.

Calculate the corresponding value of r_e.

3.

Show that the gain is given by

$$A_{in,out} = - \frac{\beta R_C}{r_\pi + (\beta +1)R_{E1}} \approx - \frac{R_C}{R_{E1}}$$

provided R_E1 >> r_e and $\beta >> 1$ (exclude effects of load resistance).

4.

Choose values of R_E1, R_E2 such that

R_E1+R_E2 = R_E

and

$$A_{in,out} = -12 \ \pm 20\%$$

(Use standard resistor values.)

5.

Calculate the input resistance

$$r_{in} = \frac{v_{in}}{i_{in}} = R_{B1} \parallel R_{B2} \parallel [(\beta+1)(r_e+R_{E1})]$$

6.

Now estimate the variation in gain A_in,out, DC operating point, and input resistance as $\beta$ ranges between its extreme values. How sensitive is your design?

7.

Use PSpice to simulate your design.

8.

Summarise your design and simulation results in Table 13.

9.

Assemble your circuit.

 

Table 13: Design, simulated and measured values.

	RE	re	RE1	RE2	Ain,out	rin
Calculated
Simulated
Measured

	IC	VCE	VBE
Calculated
Simulated
Measured

 

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