Switched capacitor circuits are very important circuits for analog design. They are used in filter applications and also for analog-to-digital conversion. In these circuits, transistors are turned on and off like switches. In this exercise, we will use the G element as a VCR model for transistors. Figure 2-13 shows the circuit of a switched capacitor amplifier. During phase Φ1, the Φ1 switches are closed and the Φ2 switches are open (See Figure 2-15). During phase Φ2, the Φ1 switches are open and the Φ2 switches are closed (See Figure 2-16). The two phases do not overlap. Their timing diagram is shown in Figure 2-14. For analysis, assume the op-amp is ideal.
1. During phase Φ1, what is the charge stored across C1? Use figure 2-15.
2. During phase Φ2,what is the charge stored across C2? Use figure 2-16.
3. Using the conservation of charge, what is the gain of this amplifier?
4. During phase Φ2, the current in C1 flows to ground to the left to discharge the capacitor. This current flows through capacitor C2 in the same direction. At the end of Φ2, is Vo positive or negative? Is this an inverting or non-inverting amplifier?
5. During phase Φ1, what does Vo equal?
6. During phase Φ2, what does Vo equal? Note: this value is sampled at the end of phase Φ1!
