On Tue, 03 May 2005 19:28:58 GMT, Ted Edwards
wrote:

Albre wrote:
I need a low frequency vco (to operate between 55 and 65 Khz) that
draws very little power (microamp supply current if possible). Goggle
...
Any suggestions?

What's the lowest supply current op-amp quad (or??) that will operate
nicely at your frequency? (I'm not up to date on micropower OAs.) If a
suitable one exists, here's a possible.

There's a very simple circuit (one OA + 4 resistors) for an amplifier
whose gain can be switched from +1 to -1. You would apply your control
voltage to its input. A fet could be used for the switch.

A second OA would be used as a simple R-C integrator with the output of
the previous applied to its input.

A two-level detector would be used to detect when the integrator output
reached V1 and V2 and its output used to drive the switch.

The slope of the integrator output is directly proportional to the input
- more voltage, steeper slope, less time to get from V1 to V2, higher
frequency.

Ted

I think the '4046 that someone suggested will be the lowest power, and
certainly simplest to set up.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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