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Common Customer Problem: Op-Amp Output Voltage Swing
By Marek LisSr Application Engineer
Texas Instruments -Tucson
![Page 2: 1 Common Customer Problem: Op-Amp Output Voltage Swing By Marek Lis Sr Application Engineer Texas Instruments -Tucson](https://reader034.vdocuments.net/reader034/viewer/2022051401/56649f1c5503460f94c332f3/html5/thumbnails/2.jpg)
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Op Amp Output Range Consideration
V3 5
Vout2-
+ +
U2 OPA140
VF2
V1 5
Vout1-
+ +
U1 OPA140
Vos
RF 1kRIN 1k
V2 -2.5
A Valid Op Amp Configuration (Input and Output within the linear range)
An Invalid Op Amp Configuration (Output outside of the linear range)
26.7uV2.5V 171.4mV
171.4mV
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REAL WORLD Outputs
V+
V+ V+
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Classic Output Stage
• Common-emitter output• Current source driver• Headroom set by
VBE+VCESAT
• Unity Gain
Q 1
Q 2
V O UT
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OPA827 – Classic Output
OPA827
OPA827
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R-to-R Output Stage
• Common Collector or Common Drain
• Headroom set by VDSsat or VCEsat
+V s
R LO AD R LO AD
+V s
-Vs-Vs
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R-to-R Output Stage
• Common Collector or Common Drain
• Headroom set by VCESAT
• Value of RLOAD affects AOL and Output Swing
+V s
R LO AD R LO AD
+V s
-Vs-Vs
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MOSFET Characteristic Curves
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Achieving Output Swing to the Negative Rail
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SS Pull Down Cheat Sheet
Part # Resistor Value
OPA335 40 kΩ
OPA340 7.5 kΩ
OPA343 7.5 kΩ
OPA348 250 kΩ
OPA350 2 kΩ
OPA353 2 kΩ
OPA333 20 kΩ