PROBLEM 101 · Beginner · A fault in: common-source amplifier
Flatline
The amplifier that does not amplify
The problem
The circuit on the canvas was built for the problem “Common-source amplifier”, but it does not meet the specification. The output sits at the supply and does not respond to the input.
Find what is wrong and repair it: change a value, move a wire or add a part. Everything the original problem asked for still applies (the targets are listed below), and the live readings and the colours of the transistors will show you where to look. Check your circuit when you think it is fixed.
The test bench
- Supply: VDD = 1.8 V.
- The test bench hangs a 200 fF load capacitor on the net named “out”.
- It applies the AC stimulus to the input source named “in”; you set that source’s DC level.
Numbers to hit
- Voltage gain at least 12 dB
- Bandwidth (−3 dB) at least 30 MHz
- Output DC level between 0.6 V and 1.4 V
- Power at most 150 µW
- Every transistor in saturation
Design it yourself
Draw the circuit on a schematic canvas, size every transistor, and see it simulated in your browser with ngspice and the SkyWater SKY130 models. Every transistor lights up green, gold or red by operating region as you move the sliders.
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