1. Signal Generation a. In PSpice, pick LM324 or uA741 (for U1 ~ U3 op-amps), construct the circuit in Figure 1. Use dual power supply of V= 9 V for the op-amps, Rref 1 and Rref_2. b. Start with the values in Table 1, simulate the transient response of the circuit. (You define the transient time duration for appropriate cycles of waveforms.) c. d. Compare the voltage at the output node of each stage (V, V and Vin). Based on your observation of the waveforms at each stage, identify and discuss the function of each block in the circuit. e. Modify R or C, observe how the frequency of the response changes. f. Change Rref 1, check how Vin changes accordingly. g. Draw conclusions on the functions of the overall circuit and individual blocks. Parameters R R R www R R4 Re R www IL www R R www Values 10 k 10 k 100 k V You may start with the following parameters for the circuit. 100 k 200 k R www C U Figure 1. A circuit to generate Vin V Ref 2 R1 6V- Parameters Rref 1 Rref 2 C C V+, V- for op-amps and voltage divider Values 10 k 20 k 1.0 uF 10 nF +9 V 2. Power Driving Circuit 1) Single transistor driver a. Connect the circuit in Figure 1 to the single MOSFET in Fig. 2. Choose IRF150 for the NMOSFET. Set R = 10 kn, RLoad = 10 2. You may include a LED as part of RLoad to visualize the effect. b. Repeat the transient simulation in last section. Observe the voltage across the load resistor RLoad (i.e. V+ - VLoad) and the current passing it. Derive the power consumption by RLoad. Find the relation of the power consumption and the duty cycle of vin. d. If RLoad is a DC motor, what will be changed with a vin in Fig. 1 that has a changing duty cycle? Comment on the connection and the result. C. e. V. RLoad - V Load + Vin RS Figure 2. Powering load using a single N-MOSFET. 2) H-Bridge driver a. Construct the circuit in Figure 3. Set Vpp =9 V. In PSpice Student, use IRF150 for NMOSFETs (M_N1-3) and IRF9140 for PMOSFETs (M_P1-3). You may choose R = 10 k2. b. Set Vin as 9 V and 0 V, respectively, check the voltage across R, i.e., Vo 2- Vo 1. Identify the direction of current passing RL. (You may use a pulse voltage source as Vin.) Connect the two circuits (Figure 1 and Figure 3) together. Perform transient analysis as done in Section 1. Check the current passing R. (Due to the nodes limit in PSpice_Student, you may need to use LTSpice for this complete simulation.) e. d. Change the value of R or C, observe how it affects Vo_1, Vo_2 and the current passing R. With certain R2 and C1, change Rref 1, observe how Vo 1,Vo 2 and IRL change accordingly. Record the waveforms (VL Vo2 - Vo 1 and IRL) of two settings of Rref 1. Calculate the power dissipated by RL. C. Vo 1 R M_P3 HE M_N2 M_N3 Vin 14 9 Voo M_P1 RL www M_P2 Vo_2 M_N1 T R Figure 3. A generic H-bridge circuit. The inverter consisted of M_P3 and M_N3 can be small signal transistors such as those in a CD4007 chip that was used in previous labs. Other MOSFETs should be power transistors.