Notes

1)
a) Amplifier is the circuit to work on signals for example gaining, buffering with transistors BJT or FETs.
b) A buffer amplifier is one that provides electrical impedance transformation from one circuit to another, with the aim of preventing the signal source from being affected by whatever currents (or voltages, for a current buffer) that the load may be produced with. The signal is 'buffered from' load currents.
c) Equalizer stage is to control frequency at a determined part. In our circuit, equalizer stage was a bandpass amplifier.
d) Gain amplifier is the device that responds to a small input signal (voltage, current, or power) and delivers a larger output signal that contains the essential waveform features of the input signal.
e) When in an amplifier circuit only one transistor is used for amplifying a weak signal, the circuit is known as single stage amplifier.
f) It’s the group of single stage amplifiers to manipulate signals.
g) First of all, since capacitor has an impedance with using them, we can eliminate some frequencies if our input signal has different frequencies. Also, it used to prevent DC current and voltage passes.
h) BJT is current-controlled device but JFET and MOSFET is voltage-controlled device. BJT is bipolar whereas, JFET and MOSFET are unipolar. BJT has base, collector, emitter terminals but FET’s has gate source and drain. BJT is cheaper than FETs. BJT has less input impedance. Also, it can provide more gain to its output.
2)
• I bought them for laboratory class, so I wasn’t needed to buy it again.
• It was cheap.
• It was suitable for our needs.
• It can work with 9V DC voltage source.
For BJT I choose 2n2222 which is NPN and for JFET I choose bf245c.
2n2222)
Power Dissipation 500mW
Collector Emitter Voltage 30V
DC Collector Current 800mA
DC Current Gain 100
Number Of Pins 3
BF245C)
Idss 12/25mA
Vgs(off) -0.25/-8V


3) For a buffer stage it’s of course possible to make it work. For gain stage, since my gain is 8 and input signal is less than 1V, 9V DC source should be enough for a pure output (without distortion).