Gain Bandwidth Product

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Gain Bandwidth Product
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Gain Bandwidth Product
Think in terms of Energy Conservation
Pout Pin PDC
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Gain Bandwidth Product
Pout Pin PDC
Now consider Power expressed in the Frequency
Domain as the Power Spectral Density Function,
S(?), and the Gain of the Op-Amp expressed as a
function of Frequency, G(?).
? G(?) S(?) d? - ? S(?) d? PDC
Pout Pin PDC
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Gain Bandwidth Product
Next, the expression
? G(?) S(?) d? - ? S(?) d? PDC
simplifies to
? G(?) 1 S(?) d? PDC
and for large G(?)
? G(?) S(?) d? PDC
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Gain Bandwidth Product
? G(?) S(?) d? PDC

• Next assume
• amplifier bandwidth is BW
• amplifier Gain (G) is constant over BW
• signal spectra (S) is constant over BW

G(?) S(?) G x S x BW
G x BW PDC / S
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Gain Bandwidth Product
G x BW PDC / S
constant term
? Gain Bandwidth Product

• Therefore if
• G increases, BW must decrease, or
• BW increases, G must decrease.

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Gain Bandwidth Product
G x BW PDC / S
constant term
? Gain Bandwidth Product
If G 1, then BW Unity-gain Bandwidth
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If G 1, then BW Unity-gain Bandwidth
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TL084
Unity-gain
Unity-gain Bandwidth
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TL084
Open loop gain
Unity gain
Unity-gain Bandwidth
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VE VIN - VIN- VOUT a VE
VIN-
VIN
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The available DC power to the amplifier can
either be put to use as high signal gain over a
limited bandwidth or limited gain over a wide
bandwidth.
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For fixed DC input power, the greatest signal
gains are achieved with weak input signals.
To get high gains in already amplified
signals (as in output stages), increased amounts
of DC power must be used.
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Differential Amplifier Circuit Analysis
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Differential Amplifier Circuit Analysis
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Differential Amplifier Circuit Analysis
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Differential Amplifier Circuit Analysis
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Differential Amplifier Circuit Analysis
? ZF / ZG
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Common Mode Rejection Ratio
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Common Mode Rejection RatioCMRR
where A is the differential mode gain and Acm is
the common mode gain
Ideally CMRR?? Typically 60 dB ? CMRR ? 120 dB
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Assumes R2 R4 and R1 R3
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Differential Amplifier Circuit Analysis with
Component Imbalance
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Differential Amplifier Circuit Analysis with
Component Imbalance
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Input and Output Impedances of Noninverting
Op-amp Configuration
The unity gain buffer input impedance is much
higher than the op-amp input impedance Rd. The
amplifier output impedance is much smaller than
the op-amp output impedance Ro.
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The available DC power to the amplifier can
either be put to use as high signal gain over a
limited bandwidth or limited gain over a wide
bandwidth.
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high signal gain over a limited bandwidth or
limited gain over a wide bandwidth.
G10,000
G10
G10
G10
G10
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Instrumentation Amplifier
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Instrumentation Amplifier Example
Burr-Brown INA118
Parameters
Gain
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ECG Amplifier System
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ECG Amplifier System
Multiple Subsystems
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ECG Amplifier System
Input Instrumentation Amplifier
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Instrumentation Amplifier
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ECG Amplifier System
Intermediate Filter and Amplifier
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ECG Amplifier System
Intermediate Filter and Amplifier
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ECG Amplifier System
Analog-to-Digital Converter
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ECG Amplifier System
Zero Reference Bias Circuit
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ECG Amplifier System
High-pass Filter for Autozeroing of DC Offset
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ECG Amplifier System
CMRR Boost Circuit (Negative Common Mode Signal
Injection on Subjects Right Leg)
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ECG Amplifier System
CMRR Boost Circuit (Negative Common Mode Signal
Injection on Subjects Right Leg)
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Common Mode Rejection RatioCMRR
where A is the differential mode gain and Acm is
the common mode gain
Ideally CMRR?? Typically 60 dB ? CMRR ? 120 dB
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ECG Amplifier System
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Instrumentation Amp
A feedback network may also be included with the
instrumentation amplifier.
vdiff v2 - v1