1. MOSFET – Common-Source Amplifier
Experiment 8
MOSFET – Common-Source Amplifier

2. 2N7000 - NMOS Drain (D) Gate (G) Source (S) NMOS CIRCUIT SYMBOL
Give a brief overview of the presentation. Describe the major focus of the presentation and why it is important.
Introduce each of the major topics.
To provide a road map for the audience, you can repeat this Overview slide throughout the presentation, highlighting the particular topic you will discuss next.
NMOS CIRCUIT SYMBOL

3. MOSFETs vs BJTs
BJTs
Three different currents in the device: IC, IB and IE
Consume a lot of power
Large size device
MOSFETs
Mostly widely used today
Low power
Very small device (nm)
Simple manufacturing process
Only 1 current, ID

4. Common Source is similar to Common Emitter (BJT)
The voltage/current gain is negative value

5. PART A MOSFET DC ANALYSIS

6. Using the DMM, measure the values of VGS, VDS and ID.
Construct the circuit of Fig. 8.1 but DO NOT CONNECT the capacitor yet and record the measured values of the resistors.
Using the DMM, measure the values of VGS, VDS and ID. G S D
VDS
VGS = 2.17 V
VDS = 5.42 V

7. To measure drain current, ID
ID = mA

8. Using the threshold voltage, VTN = 2
Using the threshold voltage, VTN = 2.1 V, please confirm that the transistor is in saturation.
(VDS > VDSsat and VDSsat = VGS - VTN)
VDSsat = VGS – VTN = 2.17 – 2.1 = 0.07 V
So is your measured VDS > VDS sat?

9. From the measured value of ID, deduce the value of the conduction parameter Kn using the drain current in saturation formula
Kn = mA / (2.17 – 2.1)2
Kn = A/V2

10. PART B Common Source Amplifier (AC Analysis)

11. By using the same circuit configuration – connecting the capacitor this time,
Set the function generator to 100 mV amplitude, 20 kHz sinusoidal wave. Connect it to vin.
Connect Channel 1 of the oscilloscope to vin and Channel 2 of the oscilloscope to vout.

13. Measure the peak-to-peak value for both input and output voltages on Channel 2 of the oscilloscope.
Calculate the value of the gain, vo / vin
vo / vin ≈ - (34 to 37)