In GENERAL, is it a good idea to use a LM4562 as a current->voltage opamp? - diyAudio
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Old 11th January 2012, 09:45 PM   #1
PelPix is offline PelPix  United States
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Default In GENERAL, is it a good idea to use a LM4562 as a current->voltage opamp?

Well, the title! In GENERAL, is it a good idea to use a LM4562 as a current->voltage opamp? It's designed to be a buffer amp, but does it work well as an I/V converter?
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Old 11th January 2012, 09:51 PM   #2
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It's not "designed to be a buffer amp"!
Is a fast, low noise, low distortion OpAmp. I did use it as I/V for TDA1541 instead of original LM833 (7V/uS).
SR 20V/uS is fast enough for audio DAC's - they usually have lower SR at output.
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Old 12th January 2012, 11:16 PM   #3
Ipanema is offline Ipanema  Malaysia
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An I/V amplifier requires unity gain stable opamp. LM4562 suitable.
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Old 14th January 2012, 02:04 AM   #4
agdr is offline agdr  United States
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Another one to consider is the LT1469:

LT1469 Product Page

http://cds.linear.com/docs/Datasheet/1469fb.pdf

LT1469 at Arrow

Linear actually shows an I-V converter as a typical application and says:

"The LT1469 is a dual, precision high speed operational amplifier with 16-bit accuracy and 900ns settling to 150μV for 10V steps. This unique blend of precision and AC performance makes the LT1469 the optimum choice for high accuracy applications such as DAC current-to-voltage conversion and ADC buffers."


Groner said about the LT1469:

"Appears to be an ideal upgrade for NE5532 amplifiers as its noise performance and quiescent current are similar"

The LT1468 is the single version of the same thing. The distributors have DIP version of the LT1468 in stock, it appears, where they only have the non-dip versions of the dual LT1469 in stock for some reason:

LT1468 DIP-8 at Digikey

Last edited by agdr; 14th January 2012 at 02:32 AM.
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Old 14th January 2012, 12:59 PM   #5
regal is offline regal  United States
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Quote:
Originally Posted by agdr View Post
Another one to consider is the LT1469:

LT1469 Product Page

http://cds.linear.com/docs/Datasheet/1469fb.pdf

LT1469 at Arrow

Linear actually shows an I-V converter as a typical application and says:

"The LT1469 is a dual, precision high speed operational amplifier with 16-bit accuracy and 900ns settling to 150μV for 10V steps. This unique blend of precision and AC performance makes the LT1469 the optimum choice for high accuracy applications such as DAC current-to-voltage conversion and ADC buffers."


Groner said about the LT1469:

"Appears to be an ideal upgrade for NE5532 amplifiers as its noise performance and quiescent current are similar"

The LT1468 is the single version of the same thing. The distributors have DIP version of the LT1468 in stock, it appears, where they only have the non-dip versions of the dual LT1469 in stock for some reason:

LT1468 DIP-8 at Digikey
Wow 90mhz bandwidth, I take it this ic opamp as I/V has a much lower input deltaZ/delta freq that has kept a lot of folks away from IC opamps for I/V? Have you tried it , any of the issues that the video opamps had when they came out and were tried for I/V?
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Old 14th January 2012, 02:49 PM   #6
agdr is offline agdr  United States
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regal: I've used the 1468 as an instrumentation amp before, but I've never used them for I/V. I've had it rattling around in my head though since seeing that writeup in the datasheet. Too bad that DIP8 version of the 1469 isn't being stocked. It would be pin compatible with the LM4562. They could be swapped back and forth in the socket. But two 1468s could be swapped back and forth with two LME49710s (the single version of the LM4562/LME49720) if the offset null pins on the 1468 are not used.

Last edited by agdr; 14th January 2012 at 02:55 PM.
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Old 14th January 2012, 03:40 PM   #7
jcx is offline jcx  United States
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if you put a C acrosss the feedback R giving a single pole low pass then there is little need for excessive slew rate - can be part of the anti-image/reconstruction filter

ideally higher frequency error V at the op amp input would then be reduced by ~ fc/GBW

with the feedback C there is a "feedthrough zero" that gives a small input Vdiff glitch at current steps due to the op amp output Z - decades old I/V app notes described the advantages of a low impedance output buffer inside the loop for op amp I/V

the op amp slew rate spec can still be a proxy for input diff pair linear operating range with degeneration, fet inputs improving both

but the low Vnoise parts can't have much degen

a compleltely new "highly linear" diff pair is used in AD8099/ADA4898 family parts - I think the ADA4898 is the best combination of specs for audio DAC I/V available today

you would need to look with a very good 'scope to see if ccs bias of the output to either rail helps - the ADA4898 has a 50 mA "linear current range" spec so you could bias at several times the fs current of most audio DAC chips
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