convert voltage to current

[alireza_s85]

i need a ic that covert the voltage to current , capable to be sink
and source

 

[Donald]

i need a ic that covert the voltage to current , capable to be sink
and source

This does not make sense !!

Please explain what you really need.

thanks

donald

 

[BobG]

i need a ic that covert the voltage to current , capable to be sink
and source

=======================
Resistor in feedback loop of an opamp voltage follower?

 

[Winfield Hill]

This does not make sense !!

Please explain what you really need.

thanks

donald

He's talking about a transconductance amplifier, which has
a voltage input and current output. You can make discrete
circuits that do this, as Tony Williams and I have written
about here on s.e.d., but an transconductance IC would be
much easier. Burr-Brown offers OTA ICs, or operational
transconductance amplifiers. The opa660 was a favorite
of mine, because of its current programmability, but TI
has just replaced it with the opa860 and opa861 parts.
http://focus.ti.com/docs/prod/folders/print/opa860.html
http://focus.ti.com/docs/prod/folders/print/opa861.html

They have a raft of application notes, which are most
easily found by searching on opa660. I find that OPA
ICs can be very useful in making precision integrators,
ramps, log converters, gyrators, etc., but Burr-Brown's
app notes concentrate on making amplifiers, etc., which
to my mind is better done with ordinary opamps.

 

[D from BC]

i need a ic that covert the voltage to current , capable to be sink
and source

An op amp with feedback off a current sensing resistor.
D from BC

 

[whit3rd]

i need a ic that covert the voltage to current , capable to be sink
and source

In addition to OTA, one can use a pair of current mirrors, op amp,
and sense resistor.

Feed program voltage to (+) input of op amp; connect (-) input
to output, and run a resistor R from output to ground. Input of
current
mirror (two matched transistors, or three if you want to be fancy)
connects to each of the power leads to the op amp. Connect both the
current mirror outputs to the load, and of course feed the
current mirrors from appropriate +/- power supplies.

Compliance should be within a volt of power supply, bipolar.

The idea is that the imbalance in the current from the op amp power
pins is due to the output current (in that sense resistor R). The sum
of the current mirrors is equal to the difference of those two
currents,
thus equal to the current in the sense resistor, which has GND at
one end and your signal (program voltage) at the other (because the op
amp is configured as a voltage follower of the input signal).

Alas, it isn't just 'an IC'; it takes at least two chips.