CE338 Digital VLSI Design 2023 Fall
Course Project Part 2
Name: Jesse Moder
Email: jmmoder@fortlewis.edu

1. Title

Sample and Hold Comparator

2. Introduction

This sample and hold circuit samples the Vin signal at the falling edge of the clock and adjusts the output voltage to the sampled Vin voltage
during the clock cycle. When connected to the comparator, the circuit samples the rising edge and adjusts Vout during the clock cycle and holds
the voltage between clock cycles. The circuit holds the voltage during the clock cycle with the stored energy in the capacitor. The faster the clock
cycle, the more closely the output voltage will match the voltage in.

3. Materials and Methods

The sample and hold circuit was created using VLSI, and the comparator circuit was imported from opamp folder on the course project page.
The logic of the circuit was exported to LTSpice for simulation.

4. Results

Figure 1 shows the sample and hold circuit and DRC.



Figure 2 shows the simulation schematic for the sample and hold circuit.



Figure 3 shows the LTSpice simulation for the sample and hold circuit.



Figure 4 shows the simulation schematic for the sample and hold connected to the comparator.



Figure 5 shows the LTSpice simulation for the sample and hold connected to the comparator.



5. Discussion

With a fast clock cycle, the voltage out closely follows the voltage in with a small deviation during the clock cycle where the voltage is held. The simulations for just the sample and hold circuit and
the sample and hold circuit with the comparator were nearly identical in tracking Vin, although the sample and hold with comparator appeared to follow Vin more closely than just the sample and hold circuit.
With just the sample and hold circuit, the signal was sampled at the falling edge and held during the clock cycle. When the comparator was connected, the signal was sampled at the rising edge and held between
clock cycles. It will be interesting to see how closely Vout follows Vin when the full circuit is constructed and simulated.