Why does the gain of a MOSFET-based common-source amplifier depend on the frequency, and why does it vary the way it does?
I did an experiment with a common source amplifier and recorded the gain at different input signal frequencies, and noticed that if the frequency was low/high, the gain would be low, but in a few central frequencies, the gain was peaked and was flatlining, much like the picture above.
I tried researching this, and a site said something about the internal capacitances in the transistor causing this effect, but the descriptions were too complex for my level of knowledge, as they started discussing BJTs and I am only really familiar with FETs.
Can someone explain the reasoning behind the fact that lower band and higher band of frequencies experience less gain than the midband frequencies?
The following is a diagram of the circuit:
The model of the transistor used is CD4007UBE from Texas Instruments, using only pins 6,7, and 8.
Here is some data: For f = 1 kHz, G = 7.26 dB For f = 10 kHz, G = 7.41 dB For f = 100 kHz, G = 7.38 dB For f = 1000 kHz, G = 6.88 dB