GATE EC 2019 Set 1 — Question 65
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Analog Circuits → Current Mirrors & Diff Amps → Active Load Diff Amp
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Question
In the circuit shown, and . The other relevant parameters are mentioned in the figure. Ignoring the effect of channel length modulation and the body effect, the value of is ______ mA (rounded off to 1 decimal place).
Correct answer
5.9 to 6.1
Solution
1.Calculate the tail current ():
The reference current is mirrored from an NMOS transistor with to the tail NMOS transistor with .2.Analyze the differential pair:
The inputs are and . Since , the NMOS transistor on the right side (with gate ) is fully ON and carries the entire tail current, while the NMOS transistor on the left side (with gate ) is OFF.3.Analyze the PMOS current mirror:
The middle PMOS transistor (with ) is diode-connected and its drain current is . This current serves as the reference for the output PMOS transistor (with ).Thus, the value of is .
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