Search found 10 matches

by Colt1911
Fri Dec 10, 2010 5:46 pm
Forum: General Discussion
Topic: HELP, Vendor for Film Capacitors
Replies: 4
Views: 986

Re: HELP, Vendor for Film Capacitors

I am not looking for $19 apiece capacitors, 50V Panasonic ECQ-P's would work just fine. Problem is that Panasonic has discontinued production and I've been unable to find a vendor that has Vishay/Sprague Orange drops in the desired values. The absolute values of the capacitors is less importance tha...
by Colt1911
Sun Dec 05, 2010 5:17 am
Forum: General Discussion
Topic: HELP, Vendor for Film Capacitors
Replies: 4
Views: 986

HELP, Vendor for Film Capacitors

:? I'm constructing a Headphone Amp with a cross-feed network and would like to use 1% film/foil or metalized film capacitors. Currently, I'm thinking radial polypropylene's would have the best balance of sonic quality, size and cost. Values are: 3.3nF, 22nF, 100nF and 1uF. Can anyone suggest a vend...
by Colt1911
Sat May 01, 2010 8:06 pm
Forum: General Discussion
Topic: :? Suggest Quad Op Amp
Replies: 4
Views: 841

Re: :? Suggest Quad Op Amp

Loop gains are 2 or less. Individual amplifier outputs are 6V or less. Power from 12 single supply. Do not need fast slew or large output current. Low supply current is a higher priority than input bias current. This is the application, R6 will be a 20K trimmer. Would an LM324 or LM224 be a good fit...
by Colt1911
Sat May 01, 2010 11:18 am
Forum: General Discussion
Topic: :? Suggest Quad Op Amp
Replies: 4
Views: 841

:? Suggest Quad Op Amp

Need a Quad Op-Amp that is negative rail input capable, is there a better choice than a pair of LM358's?
by Colt1911
Mon Apr 26, 2010 5:48 pm
Forum: General Discussion
Topic: Please help with Op Amp circuit
Replies: 9
Views: 1884

Re: Please help with Op Amp circuit

Adding a 1K pull-down to the output of the buffer works well on bread-board. The floor voltage is very close to 5V now. Thanks MrAl! :smile:
by Colt1911
Thu Apr 22, 2010 6:38 pm
Forum: General Discussion
Topic: Please help with Op Amp circuit
Replies: 9
Views: 1884

Re: Please help with Op Amp circuit

http://s3.postimage.org/OV7Zi.jpg Yes, original circuit, but with your capacitor added to the feedback loop. What I see is R3 and R4 are summing the current from the 5V reference and the output of the buffer (U1b). Current flows out of the 5V source, through R4 and R3, then into the output of U1b. ...
by Colt1911
Thu Apr 22, 2010 2:02 pm
Forum: General Discussion
Topic: Please help with Op Amp circuit
Replies: 9
Views: 1884

Re: Please help with Op Amp circuit

Please excuse the delay. I have been climbing the learning curve of LTspiceIV for the past few days. I rebuilt the original circuit on bread-board using a different LM358, just in case the first one was some how damaged, but my results were the same. That is, when the buffer input is below 0.7V the ...
by Colt1911
Mon Apr 12, 2010 3:14 pm
Forum: General Discussion
Topic: Please help with Op Amp circuit
Replies: 9
Views: 1884

Re: Please help with Op Amp circuit

Why is the Edit button hidden?
by Colt1911
Mon Apr 12, 2010 2:59 pm
Forum: General Discussion
Topic: Please help with Op Amp circuit
Replies: 9
Views: 1884

Re: Please help with Op Amp circuit

While waiting for a reply, I took a long look at the LM358 data sheet. Then I tested the whole circuit with a variety of input voltages on the low-pass filter. The original circuit misbehaves when the input is less than 0.7V. An LM358 won't sink very much current when it's output in near the negativ...
by Colt1911
Thu Apr 08, 2010 3:11 pm
Forum: General Discussion
Topic: Please help with Op Amp circuit
Replies: 9
Views: 1884

Please help with Op Amp circuit

Hi everyone :smile: I've been building hobby kits and projects from magazines for a while. This is my first try at building something from scratch. I want to use a 25KHz PWM signal to adjust the speed of a 120mm computer fan with 5V to 12V. The PWM output is an open-drain that can take 5mA at 3.3V. ...