10-04-2017, 08:18 PM
A Current-Mirror Differential Amplifier
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Prelab
The following prelab questions have been constructed to help you prepare to do the lab
efficiently. Unless otherwise stated, you should assume that like transistors are matched and
that the Early effect is negligible. Please complete these questions before you come to lab.
While you may discuss the prelab questions with your lab partner or with other students in
the class, each student in a lab group should complete the prelab assignment individually,
so that you each understand the circuit that you will be testing and what you will be doing
in the lab.
1. Consider the differential amplifier circuit shown in Fig. 5.1a comprising an nMOS differential
pair and three simple current mirrors. In answering these questions, you should
assume that all transistors of the same type are matched. Which input voltage is the
noninverting input? Which is the inverting input? Explain your reasoning briefly.
2. If the output voltage were fixed by a voltage source so that M4 and M8 are both
saturated, what would be the output current in terms of I1 and I2 if the Early effect
were negligible?
Experiment 1: Voltage Transfer Characteristics
In Capture CIS, construct a current-mirror differential amplifier, as shown in Fig. 5.1, with
an nMOS differential pair, two simple pMOS current mirrors, and a simple nMOS current
mirror. Set the bias voltage of the differential pair so that your bias current is on the order
of of microamps, which is on the high end of moderate inversion or slightly into strong
inversion.