Final Project - EE 420L 

Authored by Jacob Reed

reedj35@unlv.nevada.edu

Due Date: May 8, 2019

Design a voltage amplifier with a gain of 10 using either the ZVN3306A or ZVP3306A (or both) MOSFETs and as many resistors and capacitors as you need. You should try to get as fast a design as possible driving a 1k load, with an input resistance greater than 50k, with as large of output swing as possible. AC coupling input and output is okay as long as your design can pass a 100 Hz input signal. Your report, in html, should detail your design considerations, and measured results showing the amplifier's performance. Your design can draw no more, under quiescent conditions (no input signal), than 1 mA from a +9 V supply voltage. Your report is due at the beginning of lab on Wednesday, May 8. Access to your CMOSedu.com lab accounts will be removed at this time.

Lab Report

In order to begin this project, we needed to decide what type of amplifier topology to use that would give us a good amount of gain. The first amplifier type that comes to mind is the push-pull amplifier. From Lab 6, we know that the push-pull amplifier can provide the designer with a large amount of gain. This will be my starting point for the project.

Simulation and Theory

I will show the final design of the amplifier and explain the design considerations for the amplifier.

Figure 1: Amplifier Design

The results of the performance for the amplifier are as follows:

Figure 2: Gain of 10.23 @ 100Hz	Figure 3: Input Resistance of ~1.8MHz @ 100Hz	Figure 4: I(VDD) of 0.602mA showing current draw from power supply
Figure 5: Output Swing of approximately 4.5V	Figure 6: Rolloff frequency at 584.8kHz

Figures 2-3 above show that the amplifier meets the requirements of a voltage gain of 10.23, input resistance of 1.8MHz, and a current draw of 0.602mA, respectively.

The resistor, R1, is chosen to have such a high value because it needs to be much higher than the resistance of the load. Therefore, I chose 20MΩ. There is a large

capacitance placed at the gates of the MOSFETs, and as such, the input signal is passed to the gates of the MOSFETs. If resistors are placed at the sources of each

MOSFET, we can limit the current draw; which is desirable for the quiescent current draw design constraint. The values of the resistors in the final design were chosen

due to real-life laboratory conditions, and these resistances are what helped the amplifier meet specification.

To show the hand calculations for these resistor values, I will do the following (for a current draw of 0.6mA):

From Lab 6, I know that KP_N = 0.1233 and KP_P = 0.145.

For the final design, I ended up using a resistance of 6.75kΩ. Using circuit analysis, I can solve for the gate voltage of both MOSFETs.

Now I can solve for the source voltage of the PMOS.

Now that this has been found, I can find what kind of resistance is needed at the source of the PMOS in order to keep the current draw at 0.6mA.

This value is very close to the resistor needed which was 70Ω.

Another thing to note in the simulation schematic is that the 12pF capacitors at the input and output of the circuit are to model the scope probes used.

The 100µF capacitor in parallel with the 6.75kΩ resistor is to help with the gain of the amplifier while not affecting the quiescent current draw. The 200Ω

resistor is chosen because it is small when compared to the large capacitor, so that the time constant is not very high, but the capacitor effectively remains

a short so the resistor, R4, helps control the gain.

From Lab 6, gm_n = 18.04 mA/V and gm_p = 10.6 mA/V.

The theoretical gain of the designed amplifier is

There is a small, yet acceptable difference between the theoretical hand calculation and theoretical simulation.

For the input resistance,

Experimental Measurements

Circuit Setup

Figure 7: Circuit on a breadboard

I will show the operation and performance of this amplifier below.

Figure 8: Gain of amplifier at 100Hz	Figure 9: Output swing of approximately 5V	Figure 10: Rolloff frequency of approximately 580kHz
Figure 11: Quiescent Current Draw

The screenshots above show the gain, output swing, rolloff frequency, and quiescent current draw. The rolloff frequency is important to show so that we can observe

the speed of the amplifier. The reason why this is important is because it limits the input frequency that can be applied to the circuit, and is helpful to the circuit designer

so that they know if the amplifier is the best choice for their project. The same can be said about the output swing; it keeps the designer is aware of the limitations as far

as how much of a DC offset, or how high of an amplitude can be applied to the input of the amplifier.

For input resistance, I added a resistor of 180k to the input of the amplifier, and then measured the voltages on either side to determine the voltage drop. From that voltage

drop, I can divide it by the value of the resistor to get the input current, I_in. Once the input current is measured, I can divide the input voltage by the input current and that

will give me the input resistance.

Figure 12: Voltage (V1) at one side of the 180k resistor

Figure 13: Voltage (V2) on the other side of the 180k resistor

Parameter	Hand Calculations	Simulation	Experimental
Gain (V/V)	-15.75	-10.23	-10.3
Input Resistance (MΩ)	1.82	1.8	1.799
Quiescent Current Draw (mA)	0.6	0.602	0.885
Rolloff Frequency (kHz)		584.8	580

Conclusion

In conclusion, this project was perfect as the culmination for the students to experiment with the design of an amplifier given constraints. The simulations and hand calculations

match the experiments well, and that was satisfying as a designer. It was a difficult task in the beginning, but I was able to design an amplifier within the given design constraints,

and I feel I am a better circuit designer because of it.

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