# Analog Electronics Workshop (AEW) Apr 3, 2013 1. Contents Intro to Tools Input Offset Input and Output Limits Bandwidth Slew Rate Noise EMIRR Filtering.

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Analog Electronics Workshop (AEW) Apr 3, 2013 1

Contents Intro to Tools Input Offset Input and Output Limits Bandwidth Slew Rate Noise EMIRR Filtering 2

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Ex 1.1: Hand Calculations TypMax Vout from vos (vout_vos) Vout from Ib (vout_ib) (R7 || R8) Vout_both = vout_ib + vout_vos Vout_both = vout_ib - vout_vos 1. Use the circuit and the excerpt of the data sheet below to calculate the maximum and tpical offset form vos. 4

Ex 1.1: Solution to Hand calculation 5 This term is negligible Simplified equation has nearly the same result

Ex 1.1: Solution to Hand calculation 6

Ex 1.1: Noise and Offset PCB Setup JumperPosition JMP7, JMP8DC — Right position for DC coupling JMP1, JMP3FLT — Bottom position for no filtering. JMP2, JMP4GND — Right position for GND connection to input. JMP5, JMP6GND — Top position for input connects directly to GND. Note for this experiment Rin will be shorted. For the next experiment Rin will be connected between input and GND. U0 = OPA211 U1 = OPA277 7

Ex 1.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the I/O limitations. OPA211 OPA188 211: 127mV 188: 54mV 8

Ex 1.1: Expected Results 1. Run a “analysis>dc analysis> noise analyais>” simulation to determine total noise. CalculatedMeasuredSimulated (OPA277) Answer: (OPA211) Answer: (OPA188) Answer: 2. How did the simulated results compare to the hand calculated results. Answer: 9

Ex 1.2: Hand Calculations TypMax Vout from vos (vout_vos) Vout from Ib (vout_ib) (Rin) Vout_both = vout_ib + vout_vos Vout_both = vout_ib - vout_vos 1. Use the circuit and the excerpt of the data sheet below to calculate the maximum and tpical offset form vos. 10

Ex 1.2: Solution to Hand calculation 11

Ex 1.2: Amplifier I/O PCB Setup JumperPosition JMP7, JMP8DC — Right position for DC coupling JMP1, JMP3FLT — Top position for filtering. JMP2, JMP4GND — Right position for GND connection to input. JMP5, JMP6Rin— Bottom position for connection the input to GND via. Rin. Install OPA735 into socket U1 12

Ex 1.2: Expected Results 1. Run a “analysis>dc analysis>calculate nodal voltages>” simulation to determine the output voltage from vos. Calc (with R) Calc (no Rin) Meas (with R) Meas (no R) Sim (with R) Sim (no R) OPA277 OPA211 OPA188 2. How did the simulated results compare to the hand calculated results. Answer: 13

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Ex 2.1: Hand Calculations MinMax Common Mode Input Range -2.6V1V Output Swing Range-2.45V2.45V 1. Use excerpt from data sheet below to fill in table: 2. In this example is the limitation from input common mode range or output swing range? Answer:The positive (1V) input common mode range is the limit. The input signal is 2Vpk, so it only limits on the positive half cycle. 15

Ex 2.1: Common Mode & Output Swing Schematic The myDAQ provides +/-15V dc supplies. The circuit to the left is used to regulate the supplies to +/-2.5V. U1 is configured as a buffer for these examples. R6 is not installed and R5 is a short. In the top position J1 will connect the scope channel 0 to the output of U1 (as shown). In the bottom connection scope channel 0 is connected to the input signal for U2. U2 is configured in a gain of -34.8. This circuit will be used for bandwidth tests. 16

Ex 2.1: Amplifier I/O PCB Setup JumperPosition J2U1 Out to AI(0+) (bottom) Install OPA735 into socket U1 Set jumper J2 to top position U1 Out to AI(0+) 17

Ex 2.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the I/O limitations. 18

Ex 2.1: Expected Results Run transient analysis with the Tina circuit called “AWE-Exp1p1-opa735.tsc” Tina ResultsmyDAQ Results 1. Use the cursors on the myDAQ and Tina Spice tool to measure the amplitude of the clipped signal. Answer (calculation):+1V pk clipped positive half cycle. Answer (simulation):+1V pk clipped positive half cycle. Answer (measurement):1.75V pk clipped, but visible distortion above1.48V pk. 19

Ex 2.2: Hand Calculations MinMax Common Mode Input Range-0.5V0.5V Output Swing Range-2.0V1.3V 1. Use excerpt from data sheet below to fill in table: 2. In this example is the limitation from input common mode range or output swing range? Answer: 20

Ex 2.2: Instrument Setup Install OPA277 into socket U2 Set jumper J2 to bottom position signal generator and scope to input 21

Ex 2.2: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the I/O limitations. 22

Ex 2.2: Expected Results 1. Use the cursors on the myDAQ and Tina Spice tool to measure the amplitude of the clipped signal. Answer (calculation):-2.0V pk to +1.3V pk. Answer (simulation):-2.32V pk to 1.53V pk. (it may distort before the clip) Answer (measured):-2.43V pk to 1.59V pk (it may distort before the clip) 23

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Ex 3.1: Hand Calculations 1. Determine the bandwidth for the circuit below. Draw the closed loop gain (in dB) vs. frequency. Closed Loop Bandwidth 350kHz / 35.8 = 9.78kHz 25

Ex 3.1: Slew Rate PCB Schematic The myDAQ provides +/-15V dc supplies. The circuit to the left is used to regulate the supplies to +/-2.5V. U1 is configured as a buffer for these examples. R6 is not installed and R5 is a short. In the top position J1 will connect the scope channel 0 to the output of U1 (as shown). In the bottom connection scope channel 0 is connected to the input signal for U2. U2 is configured in a gain of -34.8. This circuit will be used for bandwidth tests. 26

Ex 3.2: Instrument Setup Install OPA333 into socket U1 Set jumper J2 to bottom position signal generator and scope to input 27

Ex 3.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the bandwidth limitations. Use the curser to determine the bandwidth (-3dB). 28

Ex 3.1: Expected Results Run transient analysis with the Tina circuit called “AWE-Exp1p1-opa333.tsc” Tina ResultsmyDAQ Results 1. Use the cursors on the myDAQ and Tina Spice tool to measure the bandwidth. Bandwidth (calculation):9.78kHz Bandwidth (simulation):16.44kHz Bandwidth (myDAQ):10kHz 29

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Ex 4.1: Hand Calculations 1. Draw the output waveform for the circuit below. 31

Ex 4.1: Slew Rate PCB Schematic The myDAQ provides +/-15V dc supplies. The circuit to the left is used to regulate the supplies to +/-2.5V. U1 is configured as a buffer for these examples. R6 is not installed and R5 is a short. In the top position J1 will connect the scope channel 0 to the output of U1 (as shown). In the bottom connection scope channel 0 is connected to the input signal for U2. U2 is configured in a gain of -34.8. This circuit will be used for bandwidth tests. 32

Ex 4.1: Amplifier I/O PCB Setup JumperPosition J2U1 Out to AI(0+) (bottom) Install OPA735 into socket U1 Set jumper J2 to top position U1 Out to AI(0+) 33

Ex 4.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the slew rate limitations. 34

Ex 4.1: Expected Results Run transient analysis with the Tina circuit called “AWE-Exp1p1-opa333.tsc” Tina ResultsmyDAQ Results 1. Use the cursors on the myDAQ and Tina Spice tool to measure the slew rate (rise / run). Slew Rate (Data Sheet):0.16V/uS Slew Rate (simulation): Slew Rate (myDAQ):(1.14V – (-1.43V)) / (20uS) = 0.129V/uS 35

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Ex 5.1: Hand Calculations 1. Determine the total rms and peak-to-peak output noise. Note: the switches are as shown (SW3 open, SW2 to GND). Total rms output noise12.49V rms Total peak-to-peak noise74.95mVpp 37

Ex 5.1 Solution to Hand Calc 38 Current noise and resistor noise are significant in this example. Reducing Rn would help overall noise. Cutoff frequency is much higher then noise corner so ignore flicker. High first stage gain so ignore noise from second stage. This could be read from the resistor noise chart.

Ex 5.1 Solution to Hand Calc 39

Ex 5.1: Amplifier I/O PCB Setup JumperPosition JMP7, JMP8AC — Right position for AC coupling JMP1, JMP3No label — Bottom position for no filtering. JMP2, JMP4GND — Right position for GND connection to input. JMP5, JMP6GND — Top position for input connects directly to GND. Note for this experiment Rin will be shorted. For the next experiment Rin will be connected between input and GND. U0 = OPA2211 U1 = OPA2188 40

Ex 5.1: Noise Schematic 41 Two copies of the same two stage amplifier is on the board. Each two stage amplifier has four jumpers to configure the circuit.

Ex 5.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the bandwidth limitations. Use the curser to determine the bandwidth (-3dB). 42

Ex 5.1: Expected Results Tina ResultsmyDAQ Results 1. Use the cursors on the myDAQ and Tina Spice tool to measure the slew rate (rise / run). Calculated Noise rms Simulated Noise rms Measured Noise rms OPA21112.5mV rms10.75mV rms8.49mV rms OPA1883.62mV rms3.59mV rms3.34mV rms 43

Ex 5.2: Hand Calculations 1. Determine the total rms and peak-to-peak output noise. Note: the switches are as shown (SW3 closed, SW2 to GND). C1 & R8 form a filter. Total rms output noise Total peak-to-peak noise 44

Ex 5.2 Solution to Hand Calc 45

Ex 5.2 Solution to Hand Calc 46

Ex 5.2: Noise PCB Setup JumperPosition JMP7, JMP8AC — Right position for AC coupling JMP1, JMP3FLT — Top position for filtering. JMP2, JMP4GND — Right position for GND connection to input. JMP5, JMP6GND — Top position for input connects directly to GND. Note for this experiment Rin will be shorted. For the next experiment Rin will be connected between input and GND. U0 = OPA211 U1 = OPA277 47

Ex 5.2: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the bandwidth limitations. Use the curser to determine the bandwidth (-3dB). 48

Ex 5.1: Expected Results Run transient analysis with the Tina circuit called “AWE-Exp1p1-opa333.tsc” Tina ResultsmyDAQ Results 1. Fill in table below. How effective is the filter in reducing noise? Measured Noise rms (filter) Calculated Noise RMS /PP (filter) Simulated Noise rms (filter) Simulated Noise rms (no filter) results from first part OPA2110.96mV0.56mV0.58mV10.75mV OPA1881.26mV1.02mV1.09mV3.59mV 49

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Ex 6.1: Hand Calculations 1. The figures below illustrate the EMIRR for two different op-amps. Assume the same magnitude and frequency (476MHz) of RF signal is applied to the circuit below. H ∆vos211 / ∆vos333 51 OPA211 EMIRR OPA188 EMIRR

Ex 6.1: Amplifier I/O PCB Setup JumperPosition JMP7, JMP8DC — Right position for DC coupling JMP1, JMP3FLT — Top position for filtering. JMP2, JMP4GND — Right position for GND connection to input. JMP5, JMP6GND — Connect “antenna” to top position. This antenna is from the amplifiers noninverting input to GND. U0 = OPA2211 U1 = OPA2188 52 Connect antenna to JMP5 & JMP6.

Ex 6.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the bandwidth limitations. Use the curser to determine the bandwidth (-3dB). 53

Ex 6.1: Expected Results myDAQ Results 1. Does the relative change in offset match the theoretical EMIRR plots from the hand calculations? 54 OPA211 output offset 2V/div OPA188 output offset 20mV/div Transceiver Keyed Answer

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Ex 7.1: Hand Calculations 1. Simulate the open loop frequency response of the circuit below (answer given). Find the frequency that we should add the zero (70.37kHz). What is the phase margin? 56 Phase margin

Ex 7.1: Hand Calculations 1. Use result from previous page to compute Riso (answer given): 57 1. Simulate open loop response (1/beta and Aol). Find the phase margin (83.6 deg).

Ex 7.1: Simulation 1. Simulate the transient response with and without Riso. 58 SW1 Closed SW1 Open

Ex 7.1: Stability PCB Schematic 59 Riso test circuit.

Ex 7.1: Amplifier I/O PCB Setup JumperPosition J2U1 Out to AI(0+) (bottom) Install OPA627 into socket U0 60 U2 U1

Ex 7.1: Instrument Setup The instrument setup above will configure the signal source and scope for the circuit below so that we can see the I/O limitations. 61

Ex 7.1: Expected Results (no Riso) Tina ResultsmyDAQ Results 62

Ex 7.2: Hand Calculations 1. The problem with this circuit is that Riso and RL form a voltage divider. With a 100mV input step, what output would you expect? Do hand calculation and use simulation with cursors to confirm the measurement. Note: the dual feedback-Riso circuit shown on the next page will solve the voltage divider issue. Answer

Ex 7.2: Stability PCB Schematic 64 Solves the issue with drop on Riso.

Ex 7.2: Instrument Setup 65 JumperPosition J2U1 Out to AI(0+) (bottom) Install OPA627 into socket U2 U2 U1

Ex 7.2: Instrument Setup 66 The instrument setup above will configure the signal source and scope for the circuit below so that we can see the I/O limitations.

Ex 7.2: Expected Results 67 Riso Riso+DF Answer 1. The figure above show the results for both the Riso and the DF-Riso. Why is the the peak-to-peak output is different ?

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8.0 Goal of Filter Lab 1.Use Filter Pro to design a Sallen-Key and Multiple Feedback filter 2.Simulate Sallen Key and Multiple Feedback filters using OPA170 and OPA241 – Sallen Key more sensitive to low GBW. – MFB less sensitive to low GBW. – OPA170, GBW = 1.2MHz – OPA241, GBW = 35kHz Measure Sallen Key and Multiple feedback filters with both op-amps. Demonstrate that MFB is less sensative then Sallen Key (both measured and simulated) 69

8.1 Filter Pro (MFB) 70

8.1 Filter Pro (MFB) 71

8.1 Filter Pro (MFB) Results 72

8.2 Filter Pro (Sallen-Key) Results 73

8.3 Tina Sim Results (all filters) 74

8.4 Hardware Setup 75 Insert OPA170 into the socket and test both Multiple Feedback and Sallen –Key. Set both sets of jumpers to S-K to test the Sallen-Key configuration and to MFB for Multiple Feedback.

Ex 8.4: Instrument Setup 76 The instrument setup above can be used for all the active filter measurements. Use the cursors to determine the cutoff frequency (-3dB point). In this example

Ex 8.4: Expected Results 77

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