CMPE 118 MECHATRONICS Operational Amplifiers (OpAmps) and Comparators Signal Conditioning, Buffering, Etc

CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS

Operational Amplifiers (OpAmps) and Comparators

Signal Conditioning, Buffering, Etc.


Operational Amplifier

+

- Characteristics

Infinte GainDraws No Input Current

Difference Amplifier

V+ > V- then the output is driven in the Positive direction

V- > V+ then the output is driven in the Negative direction


Operational Amplifier

+

- Characteristics

Infinte GainDraws No Input Current


+

-

Vout

Vin

How do we use Op-Amps then?

Negative Feedback


The Golden Rules:Apply only when the op-amp is operated:

Within its listed specifications

In Negative Feedback

1) The Inputs Draw no Current

2) The inverting and Non-inverting inputsremain at the same voltage


The Golden Rules:Apply only when the op-amp is operated:


+

- R1

R2

A

B

Vout Vin

Inverting Amplifier

Vout

R2 R1

-Vin =

Vout

Vin

R2

R1 = -


+

- R1

R2

A

B

Vout Vin

Inverting Amplifier


+

- R1

R2

A

B

Vout

Vin

Non-Inverting Amplifier

= Vin R1

Vout R1 + R2

= Vin R1

Vout R2 1 +


+

- R1

R2

A

B

Vout

Vin

Non-Inverting Amplifier


+

-

Vout

Vin

=

Non-Inverting Buffer

Vin Vout


Vin

Source Resistance

True

PerceivedVin

+

- R1

R2

A

B

Vout


What Happens to the output if we tie the two inputs together?


Input Offset Voltage

V


Input Offset Voltage Specifications


Effects of Input Offset Voltage

+ V


Input Bias Current


Input Bias Current Specifications


Can We Correct for Input Bias Current?


Does that fix the bias current problem?

Not Quite

The two bias currents are not exactly equal

This is the Input Offset Current


Does that fix the bias current problem?


Output Voltage Limitations


Output Voltage Specifications


The Importance of Test Conditions“RL = 2k”


Specifications that you shouldn’t use:


Specifications that you shouldn’t use:


+

- R1

R2

A

B

Vout

Vin

What is the minimum values for R1 & R2 if Vout is driving a 10k load and we want to achieve a 3.3V output?

LM324


Frequency Effects


Large Signal Frequency Response


0 .00 0u 20 .0 0u 40 .0 0u 60 .0 0u 80 .0 0u 10 0 .0uTim e (s )

(V

)

10.00

9.000

8.000

7.000

6.000

5.000

4.000

3.000

2.000

1.000

0 .000

ou tp u t

in pu t*10

Slew Rate Effects


0 .00 0u 2 .00 0u 4 .00 0u 6 .00 0u 8 .00 0u 10 .0 0uTim e (s )

(V

)

10.00

9.000

8.000

7.000

6.000

5.000

4.000

3.000

2.000

1.000

0 .000

ou tp u t

in pu t*10

Extreme Slew Rate Effects


P a r a m e ter L M 3 2 4 L M 6 1 4 4 L M C 6 4 8 4 L M C 6 4 9 4In p u t O ffse t Vo ltag e 7 m V 3 .3 m V 3 .7 m V 6 .8 m VIn p u t B ia s C u rren t 2 5 0 n A 5 2 6 n A 4 p A 2 0 0 p AIn p u t O ffse t C u rre n t 5 0 n A 8 0 n A 2 p A 1 0 0 p AO u tp u t Vo lta g e H i @ 1 0 K 3 .5 V 4 .8 7 VO u tp u t Vo lta g e L o @ 1 0 K 0 .0 2 V 0 .0 5 VO u tp u t Vo lta g e H i @ 2 K 3 V 4 .8 V 4 .7 V 4 .7 VO u tp u t Vo lta g e L o @ 2 K 0 .1 3 0 .2 4 V 0 .2 4 VO u tp u t Vo lta g e H i @ 6 0 0 4 .2 4 V 4 .2 4 VO u tp u t Vo lta g e L o @ 6 0 0 0 .6 5 V 0 .6 5 VU n ity G a in B a n d w id th 1 M H z 6 M H z 1 .5 M H z 1 .5 M H zS lew R a te 0 .4 2 V /S 11 V /S 0 .6 3 V /S 0 .5 V /SIn p u t C o m m o n M o d e R a n g e 0 -3 .5 V 0 -5 V 0 -5 V 0 -5 VC o st @ 1 k $ 0 .0 8 8 $ 2 .8 0 $ 1 .3 9 $ 1 .5 9Te m p e ra tu re R a n g e 0 ° – 7 0 ° C -4 0 ° – 8 5 ° C -4 0 ° – 8 5 ° C -4 0 ° – 1 2 5 ° C

A Comparison of Some Op-Amps


Questions?


What is This?


How might you use it?


Without With


How do you achieve it?


Eliminating the separate VREF


What’s going on?


Inverting Comparator Design ProcedureTrip point at 1.5V, 0.25V Hysterisis


The Non-Inverting configuration:


How does this circuit Behave?

R1=3k, R2=R3=1KVin sweeps from 0-5V


How about this one?

Vin = 5 to -5V Sin

What are the thresholds?

Documents

CMPE 118 MECHATRONICS Operational Amplifiers (OpAmps) and Comparators Signal Conditioning, Buffering, Etc