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Using a LM301 OP-AMP as a crystal accosilator.

Sorry If I missed spelled the top part. I need to know how you can use a LM301 OP-AMP or a SHMITT trigger IC to 10MHZ out from a tin can crystal. Also I need to know if this can be done at +5VDC or do you have to go to

+12VDC? Another option I am also trying to figure out is to use a 4MHZ resonator that has to out pins and a ground pin in the center.

I will use binary ripple counters to divide this down to 60HZ for a home made digital clock I am working on. The A.C. coming from the wall will be the primary clocking source but when it loses power I would like the crystal circuit to take over and continue to clock the project. I would like to keep this "cheap and dirty" if possible.

A hand drawn schamtic would help with this problem.

-- My Cat Tigger says every morning... Before my morning coffee I might as well be a DOG!

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Reply to
Scott Wiper
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I'm not familiar with the LM301, but I just finished writing a tutorial on the quartz crystal microbalance in which I use a video op-amp (AD811) for such a purpose. You can find the circuit on p.7 of the document available at

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(forget about the text which is in French, just look at the circuit and the reference related to it citing AoE).

For the schmitt trigger ... just take an inverter gate (74HCT04), connect the quartz between the input/output of an inverter, stick two capacitors between the quartz leads and ground and that should oscillate. You have to play with the value of the capacitor (in the tens of pF range) but the actual value is not critical. All this is well explained in the ARRL Handbook.

From my experience with the AD811 i had to limit myself to 5 V supply or the opamp would overheat. The CMOS inverter can be power supplied with anything from 3 V to 7 V, but chances are that at higher voltages you will jump on an overtone, so try to set the supply voltage as low as possible (for reliable operation).

The CMOS inverter is about as cheap and dirty as you can get (but not dirty enough that there is not one in the Ariane rocket ...).

Jean-Michel

Reply to
Jean-Michel Friedt

No. An LM301 has insufficient bandwidth. A Schmitt trigger inverter generally won't self-start. Use a 74HCU04, unbuffered inverter.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  Jim-T@analog_innovations.com  Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |

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Reply to
Jim Thompson

The easy way is to use a 32.768 KHz crystal from an old watch or quartz clock and divide it down to 1 second with a 15 stage counter. There is an example schematic using the 4020 14 stage counter and one additional D flip flop at:

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-Bill

Reply to
Bill Bowden

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