Data Acquisition ET 228 Chapter Subjects Covered Inverting Amplifier Inverting Adder and Audio Mixer Multichannel Amplifier Inverting Averaging Amplifier Noninverting Amplifier Voltage Follower Ideal Voltage Source Noninverting Adder Single Supply Operation Difference Amplifiers Inverting Amplifier See Figure 3-1 on page 46

Data Acquisition ET 228 Chapter Inverting Amplifier Simplifying Assumptions E d is essentially 0 if V out is not in saturation Input terminal currents in negligible Formulas for Figures 3-1, 3-2, 3-3 On Pages 46, 48, and 50 I = E i /R i I determined by the input voltage and input resistor Voltage drop across the feedback resistor Vr f = I x R f = {E i /R i } R f Output voltage - Across the load V Out = - E i {R f / R i } Output Current I Out = I + I L

Data Acquisition ET 228 Chapter Inverting Amplifier Example Problems Examples 3-1 and 3-2 on page 47 Example 3-3 on page 49 Walk through applying E i per Figure 3-3 Example Problems 3-4 on page on page on page 51 Design Procedure Choose Circuit type Pick R i (10k  is a safe choice) Calculate R f from = (gain)(R i ) Analysis Procedure Find R i Find gain from R i and R f V Out has the opposite polarity of the input

Data Acquisition ET 228 Chapter Inverting Adder and Audio Mixer Formulas for Figure 3-4 on page 52 I 1 = E 1 /R I 2 = E 2 /R I 3 = E 3 /R V Out = - {E 1 /R + E 2 /R + E 3 /R}R = - {E 1 + E 2 + E 3 } Fig 3-4 Walk through and Example Problems Example Problems 3-8 and 3-9 starting on page 52 Audio Mixer The input currents and voltages don’t interact Replace the DC voltage sources with audio sources Add an adjustable resistor in series with the input R Approximately 1/10 of R DC offset of AC signals Usually used to supply bias voltage levels needed on the output Walk through Figure 3-5 using different levels for E dc

Data Acquisition ET 228 Chapter Multichannel Amplifier Formulas for Figure 3-6 on page 55 I 1 = E 1 /R 1 I 2 = E 2 /R 2 I 3 = E 3 /R 3 V Out = - {E 1 (R f /R 1 ) + E 2 ( R f /R 2 ) + E 3 ( R f /R 3 )} A cl1 = - R f /R 1 A cl2 = - R f /R 2 A cl3 = - R f /R 3 Walk Through Fig 3-6 Example Problem 3-11 on page 56 Inverting Averaging Amplifier Make all the input resistors equal Make the feedback resistor = R/n, with n = # of inputs Example 3-12 Noninverting Amplifier Input voltages applied directly to + input

Data Acquisition ET 228 Chapter Noninverting Amplifier Formulas for Figure 3-7 I = E i /R 1 Vr f = I R f = (R f /R 1 ) E i V Out = E i + (R f /R 1 ) E i = (1 + R f /R 1 ) E i Walk through Figure 3-7 Use 5V and -5V Example Problems 3-13 and 3-14 Page 59 Voltage Follower Commonly called Source Follower Unity-Gain Amplifier Buffer Amplifier Isolation Amplifier

Data Acquisition ET 228 Chapter Voltage Follower Formulas V Out = E i A cl = V Out /E i = 1 Example 3-15 on page 62 Uses of the Voltage Follower Isolation of the quantity being measured from the measurement Walk though both circuits in Figure 3-11 on page 63 Ideal Voltage Source Characteristics Output doesn’t change regardless of the load No resistance in series with the voltage Walk through Figure 3-12 The “b” figure shows the loading due to a inverting amplifier The “c” figure shows a practical Ideal Voltage Source

Data Acquisition ET 228 Chapter Noninverting Adder Typical Circuit in Figure 3-14 Assume R = R A Inputs could be buffered with Voltage Followers Formulas V Out = E 1 + E 2 + E 3 R f = R(n-1), where n = the number of inputs E in = {E 1 + E 2 + E 3 }/3 Figure 3-14 Walk Through Single-Supply Operation Figure 3-15 Characteristics Usually used in battery operated devices Inputs can go to ground and close to the supply voltage Usually wired as Noninverting since there is only one supply

Data Acquisition ET 228 Chapter Single-Supply Operation If the input signal goes below ground (referenced to supply voltage) The input must be biased See “b” figure Difference Amplifiers Variations reviewed Subtractor Inverting-Noninverting Subtractor Figure 3-16a First an inverter inverts E 1 Then it and E 2 are feed to an inverting adder Results in V Out = E 1 - E 2

Data Acquisition ET 228 Chapter Difference Amplifiers Inverting-Noninverting Figure 3-16b Can solve using supper positioning If E 2 = 0V then V Out = 2 x E 1 If E 1 = 0V then V Out = - E 2