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current output vs voltage output

A

axr0284

Jan 1, 1970
0
Hi,
I would like to know why some DACs have current output instead of
voltage output. Is there any advantage with one or the other. Thanks.
Amish
 
J

John Larkin

Jan 1, 1970
0
Hi,
I would like to know why some DACs have current output instead of
voltage output. Is there any advantage with one or the other. Thanks.
Amish

The usual situation is that

1. The dac uses an inverted ladder architecture, where each bit switch
steers current into one node or into another. So the output is
inherently differential currents. Some architectures, like resistor
strings and delta-sigma, are inherently voltage generators, but are
usually slow.

2. The dac technology (say, cmos switches and thinfilm resistors)
isn't suitable for growing good opamps on the same chip. So they bring
out the differential currents so good, fast external bipolar opamps
can do the current-to-voltage conversion.

Current output DACs cn be very fast, gigasamples per second.

John
 
A

axr0284

Jan 1, 1970
0
2. The dac technology (say, cmos switches and thinfilm resistors)
isn't suitable for growing good opamps on the same chip.


Thanks for your answer. I was wonmdering if you could explain the
above in more detail or maybe steer me towards a website that has more
information on this. Thanks,
Amish
 
J

John Larkin

Jan 1, 1970
0
I was asking more info on the following particular subject:
The dac technology (say, cmos switches and thinfilm resistors) isn't
suitable for growing good opamps on the same chip.
Amish

I'm not an IC designer, so I can't say a lot more. But bipolar
processing makes fast, precise opamps, and CMOS makes good switches.

There are some mixed-process dacs with cmos switches and internal
opamps, but they tend to be lower, specifically slower, performance
parts.

Are there any ic design newsgroups?


John
 
A

axr0284

Jan 1, 1970
0
I'm not an IC designer, so I can't say a lot more. But bipolar
processing makes fast, precise opamps, and CMOS makes good switches.

There are some mixed-process dacs with cmos switches and internal
opamps, but they tend to be lower, specifically slower, performance
parts.

Are there any ic design newsgroups?

John- Hide quoted text -

- Show quoted text -

I'll do more research. Thanks for your time.
Amish
 
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