Transcript TELECOMMUNICATIONS TC420

Data Acquisition ET 228
Chapter 3.0 - 3.10
• Subjects Covered
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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 3.0 - 3.10
• Inverting Amplifier
• Simplifying Assumptions
• Ed is essentially 0 if Vout 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 = Ei/Ri
• I determined by the input voltage and input resistor
• Voltage drop across the feedback resistor
• Vrf = I x Rf = {Ei/Ri} Rf
• Output voltage - Across the load
• VOut = - Ei{Rf / Ri }
• Output Current
• IOut = I + IL
Data Acquisition ET 228
Chapter 3.0 - 3.10
• Inverting Amplifier
• Example Problems
• Examples 3-1 and 3-2 on page 47
• Example 3-3 on page 49
• Walk through applying Ei per Figure 3-3
• Example Problems
• 3-4 on page 49
• 3-5 on page 50
• 3-6 on page 51
• Design Procedure
• Choose Circuit type
• Pick Ri (10k is a safe choice)
• Calculate Rf from = (gain)(Ri )
• Analysis Procedure
• Find Ri
• Find gain from Ri and Rf
• VOut has the opposite polarity of the input
Data Acquisition ET 228
Chapter 3.0 - 3.10
• Inverting Adder and Audio Mixer
• Formulas for Figure 3-4 on page 52
• I1 = E1 /R
I2 = E2 /R
I3 = E3 /R
• VOut = - {E1/R + E2/R + E3/R}R = - {E1+ E2+ E3}
• 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 Edc
Data Acquisition ET 228
Chapter 3.0 - 3.10
• Multichannel Amplifier
• Formulas for Figure 3-6 on page 55
• I1 = E1 /R1
I2 = E2 /R2
I3 = E3 /R3
• VOut = - {E1 (Rf /R1) + E2 ( Rf/R2) + E3 ( Rf/R3)}
• Acl1 = - Rf /R1
Acl2 = - Rf /R2
Acl3 = - Rf /R3
• 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 3.0 - 3.10
• Noninverting Amplifier
• Formulas for Figure 3-7
• I = Ei/R1
• Vrf = I Rf = (Rf /R1) Ei
• VOut = Ei + (Rf /R1) Ei = (1 + Rf /R1) Ei
• Walk through Figure 3-7
• Use 5V and -5V
• Example Problems 3-13 and 3-14
• Page 59
• Voltage Follower
• Commonly called
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Source Follower
Unity-Gain Amplifier
Buffer Amplifier
Isolation Amplifier
Data Acquisition ET 228
Chapter 3.0 - 3.10
• Voltage Follower
• Formulas
• VOut = Ei
• Acl = VOut /Ei = 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 3.0 - 3.10
• Noninverting Adder
• Typical Circuit in Figure 3-14
• Assume R = RA
• Inputs could be buffered with Voltage Followers
• Formulas
• VOut = E1+ E2+ E3
• Rf = R(n-1), where n = the number of inputs
• Ein = {E1+ E2+ E3}/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 3.0 - 3.10
• 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
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Figure 3-16a
First an inverter inverts E1
Then it and E2 are feed to an inverting adder
Results in VOut = E1 - E2
Data Acquisition ET 228
Chapter 3.0 - 3.10
• Difference Amplifiers
• Inverting-Noninverting
• Figure 3-16b
• Can solve using supper positioning
• If E2 = 0V then VOut = 2 x E1
• If E1 = 0V then VOut = - E2