Table of Contents

• Lab 7: Op Amp Filters
• Lab 8: Op Amp Comparators
• Lab 9: Op Amp Oscillators
• Lab 10: Diodes
• Lab 11: Bipolar Junction Transistors and Amplifiers
• Lab 12: Differential Amplifiers
• Lab 13: JFETS, MOSFETS, CMOS and Applications
• Lab 14: NOT, NAND, and Flippy floppies
  • Basic Logic Gates
  • Fun With Flip-Flops

Lab 7: Op Amp Filters

• Download Lab 7: Op Amp Filters.
• Skip part 1-1 (integrator with a mechanical switch), and begin with part 1-2. First, however, trim the input offset potential to zero.
• Compare the active band-pass filter to a passive band-pass filter. A useful, quantitative tool for comparing the frequency response of band-pass filters is the quality factors The components for the active band-pass filter are C1=C2=20pF, R1=2kOhms, R2=200kOhms. You can use the same components for the passive band-pass filter, or create a better passive band-pass filter by lowering the breakpoint frequency of the low-pass filter component, and raising the breakpoint frequency of the high-pass filter component, essentially "pinching off" the desired frequency.
• Last day to work on Lab ,7 is Tuesday, 14 January.
• Turn-in Requirements: Rough Draft Only

Lab 8: Op Amp Comparators

• Download Lab 8: Op Amp Comparators.
• Work fast during this lab, we will have 3 days to complete it and you should have the transimpedance amplifier built by the end of the second lab day. You will need to come in outside of class.
• For the Schmitt Trigger application in part 3 of the lab manual, use a TIP120 transistor to add current to the heating resistor, and use the AD592 temperature transducer, instead of the AD590.
• 3 lab days allowed. Lab begin date: 16 Jan. 2014, Lab end date: 23 Jan. 2014
• Turn-in Requirements: Rough draft required (due 27 Jan. 2014), Final draft required (due 31 Jan. 2014).

Lab 9: Op Amp Oscillators

• Download Lab 9: Op Amp Oscillators.
• It is easy to establish the operating parameters for the astable multivibrator.
• The VCO described vaguely in the handout is difficult to build. Here is the circuit including the 2N4123 bipolar transistor switch. Try this simpler circuit (updated 27 Jan 2012). Some observations: output for Vref = 6 V, expanded output for Vref = 6 V, V+ input signal for Vref = 6 V, V+ input signal and output for Vref = 6 V, V+ input signal and output for Vref = 3 V.
• Use simulate_pso.py (updated 29 Jan 2012) to simulate the four-stage CR phase shift oscillator (PSO). The first function describes the complete filter and inverting op amp circuit. The second function describes just the inverting op amp circuit. The third describes just the four-stage series CR filter. Run all three simulations and compare to the observed behavior of your circuit. This program differs from simulate.py in the function CalculateResponse. A patch has been made to detect and correct for the possible mathematical artifact of a phase shift when angle(z) is used. The titles of the graphs can be horrendously long because they completely describe the circuit, so a switch has been installed to enable or disable the display of the complete circuit explanation at the bottom of the graph window. Set explain=True or explain=False in the function call. For the 4-stage CR PSO: power, phase; power with explanation; phase with explanation. Oscillation will occur at the frequency for which the round trip power gain is 0 dB and the round trip phase shift is 0. In the real physical circuit, it might be necessary to use a pot to tweak the gain and a pot or a variable capacitor to tweak the phase shift of the first CR stage after the opamp. For the two-stage RC PSO, complete the two stage RC PSO function in the program, run the simulation and compare to the observed behavior.
• 3 lab days allowed. Lab begin date: 28 Jan. 2014, Lab end date: 4 Feb. 2014
• Turn-in Requirements: Rough draft required (due 7 Feb. 2014)

Lab 10: Diodes

• Download Lab 10: Diodes.
• Read about diodes in Ch. 4 of Simpson.
• Silcon (Si) diodes: Several to choose from--make note of the current limits and choose your own.
• Schottky Barrier diodes: Watch your current limit, make sure to at least roughly calculate the minimum current limiting resistance.
• Zener: There are many Zener diodes in the storage unit, use the 1N4733A 5.1V Zener diode set out on the counter.
• LED: Choose one closest to your favorite color.
• Photodiode: To function in photoconductive mode, photodiodes need to be reverse biased. Make sure to carefully look at the circuit diagram.
• Using the diode I(V) simulation program, the simulated I(v) curve and I(v) curve close to V = 0 can be compared to observations.
• Using the diode I(V) time-domain simulation program, the simulated time-domain V(t) and I(t) curves and Fourier transform spectra can be compared to observations.
• Extra diode concepts and applications (no lab report required):
  • A diode behaves as a nonlinear source for harmonics of a fundamental frequency applied to a circuit. As an additional investigation, experiment with a single diode in series with a resistor and the parallel combination of opposite diodes in series with a resistor, as described by these circuit diagrams. Explore both cases of a DC potential applied across the circuit and of a sinusoidal potential applied across the circuit. The simulations below were produced by diode_nonlinear_source.py. Modify the few lines in Main() to simulate the experiments.
    • Acquire and analyze the following data sets for the single diode configuration: V_R and V_D for a slowly varying input potential (simulation), V_R and V_D vs time for a sinusoidal input (simulation), V_R vs V_in for a sinusoidal input (simulation), V_R and V_in power spectra for a sinusoidal input (simulation).
    • Acquire and analyze the following data sets for the parallel opposite diodes configuration: V_R and V_D for a slowly varying input potential (simulation), V_R and V_D vs time for a sinusoidal input (simulation), V_R vs V_in for a sinusoidal input (simulation), V_R and V_in power spectra for a sinusoidal input (simulation).
    • Actual data for a single 1N4150 diode in series with a 1.2 kΩ resistor: input and output across R.
    • Actual data for parallel, oppositely-oriented 1N4150 diodes in series with a 1.2 kΩ resistor: input and output across R.
    • The profound difference among the power spectra for V_in, V_R for one diode and V_R for two diodes is a consequence of the symmetry of the response of the circuits. When the response of the circuit is nonlinear and symmetric when graphed against the input signal, as for the case of parallel and opposite diodes, then only the odd harmonics are present. When the response is asymmetric (no apparent symmetry), as it is for the case of a single diode, then all the harmonics are present, the most prominent being the second harmonic. The electromagnetic wave analogs of these phenomena are second harmonic generation and multi-wave mixing in general, observable at all frequencies.
  • A Thermoelectric or Peltier device can be used to pump thermal power from a cold reservoir to a hot reservoir with an efficiency below 4%. Alternatively, it can be used to generate electrical power from a thermal differential. It consists of parallel combinations of low band gap diodes in series. The CUI CP40336 can sink at most 37 W at 15 V and 4 A or create a temperature difference of -70 kelvin. This application note is useful. Being careful of the polarity, apply about 5 VDC up to about 0.1 A while holding the two sides between your fingers. Turn off the power after a few seconds. For prolonged use at higher power, hold the hot side down on a metal heat sink. Measure the temperature of the cold side at powers below the limit. How cold does it get? Draw a band energy diagram that explains the behavior of this device.
  • Photovoltaic devices convert solar radiation to electrical power based on the directionality and band gap energy provided by a pn junction. The IXYS KXOB22-12X1 is a single junction, single crystal Si device with up to 22% efficiency. The Sanyo Energy AM-1456CA consists of three amorphous silicon (a-Si) pn junctions in series and is a low efficiency device. For either device, measure the open-circuit potential and the potential under a load of 100 Ω or less. Use a bright flashlight.
• 2 lab days allowed. Lab begin date: 11 Feb. 2014, Lab end date: 13 Feb. 2014
• Turn-in Requirements: Rough draft required (due 19 Feb. 2014), Final draft required (due 24 Feb. 2014).

Lab 11: Bipolar Junction Transistors and Amplifiers

• Follow these instructions to build two difference amplifiers and use them to measure β.
• Or use a clever transimpedance op-amp measurement (Circuit Diagram) to obtain all transistor information at once.
• Follow the instructions given in class to explore the behavior of a DC-coupled common emitter amplifier.
• Modify the amplifier to allow for AC-coupling and biasing using a resistive divider and V_cc.
• Add R_E in order to stabilize the transistor if temperature fluctuations occur.
• Calculate the exact gain as v_out/v_in and compare it to the measured value at 1 kHz. How does the gain vary as the frequency is increased all the way to 20 MHz? Use scan_2.py to obtain this data.
• Build a follower or common collector amplifier. Using a positive sinewave as an input signal, measure the gain and compare to a theoretical expression.
• Build a current mirror using two 2N3904 BJTs and show that the current in the mirror is correct to within a factor of the ratio of the two βs.

Lab 12: Differential Amplifiers

• There is insufficient time to do this lab, but you should read it: Laboratory handout.

Lab 13: JFETS, MOSFETS, CMOS and Applications

• lab 13
• notes
• Read about FETs in Chapter 6 of Simpson.
For the 2N5459 JFET, use one difference amplifier across the drain resistor R to measure I_D, and set V_DD = 10 V. Find V_po, the pinch-off value of V_GS. For several values of 0 > VGS > V_po, use V_DD(t) = V_o sin(ωt) and plot I_DS vs V_DS. For each value of V_GS is the channel Ohmic over any range of V_DS? For this work, use ν = 1 kHz and observe V_DS on channel 1 and the output of the difference amplifier (which is proportional to I_DS) on channel 2. Display the data in both yt and xy modes. Increase ν by hand to 20 MHz and observe the behavior of the I_DS vs V_DS graphs. Create a theoretical model for I_D(V_DS) and compare it to the experimental measurements.
• Look at the suggested circuit to measure R_channel for the n-channel enhancement-mode MOSFET BS170. On the AFG3012B, set V_GS(t) to be an amplitude with an offset. If you use AC coupling for V_GS on the scope, then the vgs_offset parameter will be the offset on the FG, otherwise, it will be 0. Some data: wide range, medium range, small range, minimum range.
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• Example of a common source amplifier with 10 MOhm input impedance: specifications and schematic, power spectrum, phase. Note that there is a CR high pass filter which leads to no gain below 100 Hz, useful for eliminating 60 Hz noise. The bypass capacitor on the source, 0.27 uF, was chosen to maximize the gain above 1 kHz. If a smaller capacitance is used, there will be a plateau of lower gain in the 1 to 10 kHz region. The drop off in gain above 1 MHz arises from the characteristic time R_D*C_cable. Also note that the phase measurement is shifted by -π.
• Before building a similar amplifier, refer to your I_D vs V_GS data to determine the appropriate value of V_GS and I_D. Then calculate the required value of R_S. Check the DC operating point value of V_GS, and make sure that V_DS > 2 V. Adjust R_D and R_S as necessary.
• Common FET Characteristics
• Build a Colpitts Oscillator using the 2N5459 JFET:
  • Read about the Colpitts oscillator in section 7.5 of Simpson.
  • Use simulate_colpitts_osc.py to estimate the phase and power of a 17 MHz oscillator.
  • Use these updated programs (rename your current version for future reference): response_plot.py (Use run=9 and change the path and file name. When queries for the Q, try about 1500 so that the simulation matches your data.).
  • Build a 17 MHz oscillator using this generic circuit, which was discussed in class. Acquire a waveform from the oscilloscope and plot the data as power density vs log(ν) and vs. ν. What is the THD? What is Q = ω/Δω? By how much does the frequency drift in one hour? Connect your oscillator to the spectrum analyzer and determine Q and the drift per minute.
  • Replace the two inductors with lower value inductors of only a few finger loops. Create the highest possible oscillator.
• Specifications for a 170 MHz oscillator. This waveform was taken at 5.0 ns/div, the fastest horizontal scale. Note that the TDS1012B digitizes at 1 Gsps. The following power spectra use a Hanning window. Acquiring a waveform over 170 cycles yields a power spectrum squeezed into a small part of the spectrum because of the unphysical range of very high frequencies. This 420 cycle power spectrum is more useful, but suffers from digitization artifacts arising from too few data points per cycle, as shown here. The linear spectrum compares well to a simulated Lorentzian spectrum with Q = 340. The Q determined from a spectrum analyzer is actually about 10,000.
• Specifications for a 240 MHz oscillator. This waveform was taken at 5.0 ns/div, the fastest horizontal scale. The following power spectrum use a Hanning window. Acquiring a waveform over 240 cycles yields a power spectrum squeezed into a small part of the spectrum because of the unphysical range of very high frequencies. The linear spectrum. The Q determined from a spectrum analyzer is actually about 10,000.
• A tweaked version of the same circuit oscillated at 244.4 MHz with a slow drift of about 1 KHz per minute after thermal stabilization. To achieve decent resolution in the power spectrum, waveforms of about 240 cycles were joined together in sets of 100, 200, 400 and 800, with each waveform consisting of 2500 points.
• 3 lab days allowed. Lab begin date: 25 Feb. 2014, Lab end date: 4 Mar. 2014
• Turn-in Requirements: Rough draft required (due 7 Mar. 2014), Final draft Required (due 21 March 12pm<\b> 2014