EE3110 AEC4_Operational Amplifiers_2007

EE3110 AEC4_Operational Amplifiers_2007 - 4 Operational...

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Unformatted text preview: 4 Operational Amplifiers (Op-Amp) 4.1 Op-Amp types v i v in v in v ip v ip v o v o v op v on Single ended input, single ended output. Floating input, single ended output. Floating input, floating output. (+) (-)-V CC (+) (-)- + +V CC v ip v on v op v in Primitive Op-Amp 4.2 Floating Input, Single Ended Output Op-Amp Static input/output characteristics v in +V CC-V CC v ip v o v =v -v id ip in v (neg) sat v (pos) sat v o Dynamic characteristics : frequency response 10 6 10 5 10 4 10 3 10 2 10 1 1 10 100 1k 10k 100k 1M 10M Slope : 6dB/ octave or 20dB/ decade A v f c A v f c f B f(Hz) The open loop gain v A is finite and decreases with frequency at the cut-off frequency c f . When negative feedback is used, bandwidth c f can be increased at the expense of lower gain v A . In general : GBW f f A f A B c v c v = = = , the gain bandwidth product 741 op-amp typical values : MHz f Hz f A B c v 1 5 000 , 200 Slew rate v ip v o The output of an op-amp cannot change faster than a certain value (0.5V/ s for 741) known as the slew rate. The response is a linear change because the mechanism of slewing involves the charging of compensation capacitors (internal to the 741) by what looks like a constant current source. Slew rate dt t dv S ) ( = V/s Common Mode Rejection Ratio (CMRR) common mode input 2 in ip c v v v + = differential mode input in ip d v v v- = common mode gain = = d v c o c v v A common mode rejection ratio c v A A CMRR o = this simplified definition is a measure of an amplifiers ability to reject unwanted signals that are common to both inputs. The Ideal Op-Amp v ip r o r d v =v -v d ip in A v v d v in v o Paramete r Ideal Bipolar FET i/p A...
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This note was uploaded on 01/11/2011 for the course EE 3110 taught by Professor Wingshingchan during the Fall '08 term at City University of Hong Kong.

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EE3110 AEC4_Operational Amplifiers_2007 - 4 Operational...

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