EE 2212

EXPERIMENT 5

15 October 2020

The Half Wave Rectifier and Precision Rectification

Lab Report Due: Thursday, 22 October

PURPOSE

Ø Use of the HANTEK 2D42 DMM to Test Diodes

Ø Implement designs of the half wave rectifier circuit and measure time domain characteristics and the transfer characteristic, vo(t) vs. vs(t).

Ø Measure and compute ripple voltage as a percentage and as an rms value. Compare individual diode results and circuit results using SPICE simulations.

COMPONENTS

Ø 1N4002 or the 1N4001 Diode (Use the 1N4002 diode model in the SPICE library)

Ø 2 kΩ and 1 kΩ resistors

Ø 0.1 μF, 1μF, and 10μF capacitors Actual values not critical since you are just showing the “filtering/smoothing” effect to minimize ripple voltage.

PROCEDURE

Ø You can use the HANTEK 2D42 DMM to measure the functionality of a junction; specifically the 1N4002.

· Turn on the HANTEK and press the “DMM” key.

· Toggle the F4 menu to the 4^th screen, 4/4

· Toggle F1 to highlight the diode symbol

· Connect the DMM leads (Forward and Reverse) and verify forward and reverse bias diode operation

Ø Examine the model characteristics for the 1N4002 PSPICE, which can be

found by selecting the device and then Edit_Model…_Edit Instance Model (Text)… You will use this information for comparing to your measurements.

Half-Wave Rectifier

Ø Refer to Figure 1. Your signal source to a 2.5 volt zero-to-peak 1000 Hz sinusoid.

· The HANTEK 2D42 AWG (Signal Generator) has a limited range of 5 volts peak-to-peak or 2.5 volts which does limit the types of experiments we can perform

· Set up the AWG leads as shown in Figure 1. Be sure the AWG is on “Green” icon is on.

· Toggle F4 to Screen 1. Then toggle F1 to Sine; toggle F2 to set frequency of 1 kHz using the arrow keys

· Toggle F4 to Screen 2 and then toggle F2 and adjust offset to 0 volts using the left-right arrow keys.

Ø Perform a SPICE transient analysis simulation and observe the half-wave rectified output like we did in a class demonstration. Refer to PowerPoint class notes. Also note the effect of the diode offset voltage when you compare the input and output waveforms. Observe and plot Vout(t) and the transfer characteristic, Vo vs Vs(t).

· To obtain the transfer characteristic, Press the “Time” button and toggle to X-Y from Y-T screen

Ø Experimentally observe the operation on the oscilloscope in both the time domain and as a transfer function.

Ø Now we want to “smooth out” the pulsating DC by using capacitors. Place a C across the 1 kΩ resistor. Use three values of C to illustrate the change in the ripple voltage by measuring Vout(t). Explain the differences in these measurements and explain what these measurements are illustrating. Use your diode model and check your lab measurements using SPICE. Observe that ripple voltage is defined as either the (DV/Vpeak) x 100% or as (Vrms or as Vrms of the output voltage/Vpeak)x 100% )x 100%. Watch your polarity on the electrolytic capacitors or else Also, since electrolytic capacitors have a broad tolerance, their values must be checked on the capacitance meter to obtain accurate results.

PRECISION RECTIFICATION-DIGITAL SIGNAL PROCESSING FUNCTION (DSP)

Ø Precision rectification is used in DSP (Digital Signal Processing) applications where the “switch” and absolute value function needs to be implemented but there must be a minimization of the effect of the diode forward voltage. Can we design a circuit that minimizes the 0.7 volt forward voltage drop? Of course the answer is yes or why would we spend the time in the lab demonstrating this!

Ø Measure the transfer characteristic, Vout as a function of Vin of the circuit shown in Figure 2(a). Use either the 1N4001 or 1N4002 diodes. Pay particular attention to the effect of the diode offset voltage when you measure the transfer characteristic.. Now construct the circuit shown in Figure 2(b). Use ±9 volts (Two battery packs) for the mA 741 operational amplifier. Measure the transfer characteristic and compare to the results in Figure 2(a). Justify the term “precision rectification” when applied to the circuit in Figure 2(b). Refer to Section 12.8 of the text, page 745, Figure 12.51 for additional information. Simulate in SPICE showing the transfer characteristic.

Again, AWG output red lead and Ch. 1 red lead connect to Vin and the Channel 2 Red lead connects to Vout.

As with the half-wave rectifier, you can toggle between Y-T and X-Y for time domain and transfer characteristic respectively.

Ø =

Figure 2 (a) and Figure 2 (b)

More Good Stuff-The 10 Commandments (Sort of archaic prose but fun). From an anonymous posting om the side of a file cabinet in an unnamed industrial laboratory.