Feedback in Amplifiers - Revision history

Michaelvier at 18:06, 20 January 2010

2010-01-20T18:06:02Z

← Older revision		Revision as of 11:06, 20 January 2010
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	== Feedback ==		== Feedback ==
	[[Image:Inverting_Op_Amp.jpg\|300px\|thumb\|right\|This negative feedback Op Amp setup will amplify and invert Vin on its way to Vout. When V<sub>in</sub> increases, the output from the Op Amp becomes negative. With the appropriate value for R<sub>1</sub> (a very large resistance since gain will be high), V<sub>ToAmp</sub> will be pulled down until equilibrium is reached and V<sub>ToAmp</sub>=0.]]		[[Image:Inverting_Op_Amp.jpg\|300px\|thumb\|right\|This negative feedback Op Amp setup will amplify and invert Vin on its way to Vout. When V<sub>in</sub> increases, the output from the Op Amp becomes negative. With the appropriate value for R<sub>1</sub> (a very large resistance since gain will be high), V<sub>ToAmp</sub> will be pulled down until equilibrium is reached and V<sub>ToAmp</sub>=0.]]
	Since the gain in an op amp is extremely high, usually hundreds of thousands in magnitude<ref>"Op Amps." ''www.williamson-labs.com.'' Williams Labs, 2007. Web. 10 Jan 2010.</ref>, very small differences in input voltages can cause the output to reach the amp's maximum gain. This makes op amps useful as voltage comparators when no feedback is present. But for most practical uses, feedback from the output into the inverted input is needed in order to control the input voltage difference and keep the output from reaching its maximum. When the positive input gets higher, the output goes up, causing the inverted input to rise, thus re-lowering the output. Output and input change for a while as they stabilize at their new values, at which point the positive and inverted inputs are equal ~~and~~ the ~~output~~ is 0.		Since the gain in an op amp is extremely high, usually hundreds of thousands in magnitude<ref>"Op Amps." ''www.williamson-labs.com.'' Williams Labs, 2007. Web. 10 Jan 2010.</ref>, very small differences in input voltages can cause the output to reach the amp's maximum gain. This makes op amps useful as voltage comparators when no feedback is present. But for most practical uses, feedback from the output into the inverted input is needed in order to control the input voltage difference and keep the output from reaching its maximum. When the positive input gets higher, the output goes up, causing the inverted input to rise, thus re-lowering the output. Output and input change for a while as they stabilize at their new values, at which point the positive and inverted inputs are very nearly equal. Since the gain is extremely large, this minute difference in input voltages, which we approximate to be 0, amplifies to give a voltage at Vout.

	== References ==		== References ==

Benjamin.henry: /* Reviewers */

2010-01-13T02:14:15Z

Reviewers

← Older revision		Revision as of 19:14, 12 January 2010
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	**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.		**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.
	*"The output is 0" - Feedback paragraph, last line. Are you sure?		*"The output is 0" - Feedback paragraph, last line. Are you sure?
			*[[Ben Henry\|Henry,Ben]]

	==Readers==		==Readers==

Fonggr: /* Reviewers */

2010-01-12T21:55:03Z

Reviewers

← Older revision		Revision as of 14:55, 12 January 2010
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	**URL Caption: Op Amps		**URL Caption: Op Amps
	**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.		**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.
	*"The output is 0"		*"The output is 0" - Feedback paragraph, last line. Are you sure?

	==Readers==		==Readers==

Fonggr: /* Reviewers */

2010-01-12T21:54:39Z

Reviewers

← Older revision		Revision as of 14:54, 12 January 2010
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	**URL Caption: Op Amps		**URL Caption: Op Amps
	**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.		**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.
			*"The output is 0"

	==Readers==		==Readers==

Fonggr: /* Reviewers */

2010-01-12T21:48:05Z

Reviewers

← Older revision		Revision as of 14:48, 12 January 2010
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	[[Greg Fong]]		[[Greg Fong]]
	*<math>V_{out}=G(V_+-V_-)\,</math>		*<math>V_{out}=G(V_+-V_-)\,</math>
	*< ref>[URL:URL caption]- Notes </ref>		*< ref>[URL:URL caption] Notes </ref>
	**URL:www.williamson-labs.com		**URL:www.williamson-labs.com
	**URL Caption: Op Amps		**URL Caption: Op Amps

Fonggr: /* Reviewers */

2010-01-12T21:41:15Z

Reviewers

← Older revision		Revision as of 14:41, 12 January 2010
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	*<math>V_{out}=G(V_+-V_-)\,</math>		*<math>V_{out}=G(V_+-V_-)\,</math>
	*< ref>[URL:URL caption]- Notes </ref>		*< ref>[URL:URL caption]- Notes </ref>
	**URL:		**URL:www.williamson-labs.com
			**URL Caption: Op Amps
			**Notes: Williams Labs, 2007. Wed. 10 Jan 2010.

	==Readers==		==Readers==

Fonggr: /* Reviewers */

2010-01-12T21:39:36Z

Reviewers

← Older revision		Revision as of 14:39, 12 January 2010
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	[[Greg Fong]]		[[Greg Fong]]
	*<math>V_{out}=G(V_+-V_-)\,</math>		*<math>V_{out}=G(V_+-V_-)\,</math>
	*<ref>[URL:URL caption]- Notes </ref>		*< ref>[URL:URL caption]- Notes </ref>
			**URL:

	==Readers==		==Readers==

Fonggr: /* Reviewers */

2010-01-12T21:36:21Z

Reviewers

← Older revision		Revision as of 14:36, 12 January 2010
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	[[Greg Fong]]		[[Greg Fong]]
	*<math>V_{out}=G(V_+-V_-)\,</math>		*<math>V_{out}=G(V_+-V_-)\,</math>
			*<ref>[URL:URL caption]- Notes </ref>

	==Readers==		==Readers==

Fonggr at 21:23, 12 January 2010

2010-01-12T21:23:20Z

← Older revision		Revision as of 14:23, 12 January 2010
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	==Reviewers==		==Reviewers==
			[[Greg Fong]]
			*<math>V_{out}=G(V_+-V_-)\,</math>
	==Readers==		==Readers==

Michaelvier at 07:37, 12 January 2010

2010-01-12T07:37:09Z

← Older revision		Revision as of 00:37, 12 January 2010
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	==Contributers==		==Contributers==

	--[[~~User:~~Vier, Michael\|Michael Vier]] (Author)		--[[Vier, Michael\|Michael Vier]] (Author)

	==Reviewers==		==Reviewers==

	==Readers==		==Readers==