Current Mirror Current Source and Differential Amp.

The circuit in Fig.6.1 is a current mirror. The circuit works as a current source where the magnitude of the current is determined by R_p. By choosing R_p, you can determine the current through Q1 by KVL. Since V_BE1=V_BE2, the current through Q2 is the same as the current through Q1. The current through Q1 is the current source current. (see class notes and text).

1.

Verify that the current through R2 is always approximately 1mA, for the 100, 1k, and 5k loads.

2.

Design a current mirror which acts as a constant source providing 2mA. Keep the supply voltage at 10.7V.

3.

Try to determine a method to measure the output resistance of the current source.

4.

Design and build a differential amp with single ended gain of approximately 100. Start by designing a current mirror that provides 2mA. Then choose appropriate values for R_C to give the required gain. (Review lab 5 for ideas)

  

Figure 6.1: Current Mirror