UAF42: Band Pass Filter

Christopher James

Part Number: UAF42
Other Parts Discussed in Thread: LM4766, LM555

The Bandpass Filter UAF42 diagram is based upon the plastic 14 Pin Package and there does not appear to be one for the 16 Pin SOIC surface mount package.

I have attached an amended version of the filter with what I believe are the correct Pins for the 16 Pin package. Can you, please confirm or otherwise?

My input frequency voltage is only circa 1.5v but I am proposing to run the UAF42 from a 15volt parallel rail supply. Will this present a problem?

Should I have a decoupling capacitor between V+ Pin 11 and Ground , and if so will a 1uF capacitor be adequate?

On some of the UAF42 filter diagrams VIN2 is connected to ground Pin 12 via a RQ which varies in value. The two square wave frequencies I am converting into sine wave are circa 40Hz and circa 530Hz. Should I add a decoupling resistor between Pin 4 and Ground, and if so, what size(s) should I use, please?

Thank you so very much.

CJJ

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Christopher,

I hope the following simulation will answer your questions:

christopher_uaf42e.TSC

No, I would not add a cap in parallel to RQ.

Connect a decoupling cap from each supply voltage to signal ground. Use at least 100nF/X7R.

Kai

0 Christopher James over 5 years ago in reply to kai klaas69

Intellectual 880 points

Dear Kai,

I cannot thank you enough, I am so very grateful!

I have little understanding of electronics per se, and thus with our technician poorly in hospital I have been floundering.

Thus, your kind assistance cannot have come at a better time.

Thank you once again.

Christopher J James
Director

PS May I substitute UAF42AUE4 for the UAF42E in the Diagram, please?

0 Christopher James over 5 years ago in reply to kai klaas69

Intellectual 880 points

Dear kai,

Is it too much to ask how I might connect the output from Pin 8 to an LM4766 amplifier as recommended, please?

Can you also, please advise what external Resistors and Capacitors would be required?

My final destination has an impedance of typically 175 to 200 Ohms.

I cannot thank you enough for your kind help.

I am sincerely grateful.

Christopher J James

0 kai klaas69 over 5 years ago in reply to Christopher James

Guru 140200 points

Hi Christopher,

I would use this circuit:

Choose RM=18k and CM=100µF for the muting circuit. You can close S1 permamently, if you don't want to mute the LM4766 by hand. For Rv I would take a multiturn cermet trimmer from Bourns.

Connect pin 8 of UAF42 to the audio input terminal of above circuit. Turn Rv fully down before you power on the UAF42 and LM4766. Then, adjust the output level as desired.

Kai

0 Christopher James over 5 years ago in reply to kai klaas69

Intellectual 880 points

Dear Kai,

Amongst my colleagues, we define people either as "service to others" or "service to self". You are without debt a "service to others" for which I am exceedingly grateful to you.

You will probably have seen my request for help with the 555 timer circuit, which is the last unknown for me.

Would it be possible for you to evaluate the values of Ra Rb and Rl for the LM555, please? I also assume that the output from LM555 is at Pin3?

Thank you once again.
Christopher J James

0 Christopher James over 5 years ago in reply to kai klaas69

Intellectual 880 points

Dear Kai,

I neglected to add, the timing interval I wish to achieve, to switch from one frequency to the other is 5 minutes, please.

Thank you so much.

Christopher

0 Raymond Zhang1 over 5 years ago in reply to Christopher James

TI__Guru* 77501 points

Hi Christopher,

Enclosed are two square wave generators. The generated frequency is pretty close to 40.6Hz and 528Hz, but they may need some fine tuning.

Best,

Raymond

LM555 528Hz squarewave 02032020.TSC

LM555 40.6Hz squarewave 02032020.TSC

0 Christopher James over 5 years ago in reply to Raymond Zhang1

Intellectual 880 points

Dear Raymond,

I used to run 555 timer circuits, thank you, until I started to programme Epson Crystals. The circuit only involves a voltage reduction, the crystal, a Ripple Counter and a few capacitors and it is accurate for both frequencies to 4 decimal places.

I will certainly look at the circuits, but I am loath to change what is working non stop 24/7 for the past two plus years.

I realise at some point in the future the availabilty of the Epson Crystal will fry up, but that is hopefully a liitle way off as I have over 1000 in stock.

Christopher

PS Would it be possible to respond to my queries about the links carrying RL, please?

0 Christopher James over 5 years ago in reply to kai klaas69

Intellectual 880 points

Dear Kai,

I wanted to thank you again for all the help that you have so kindly given me.

I thought you might like to see what is hopefully my final circuit for the UAF42.

Thank you once again.

Christopher

0 kai klaas69 over 5 years ago in reply to Christopher James

Guru 140200 points

Good luck, Christopher!

Kai

0 Christopher James over 5 years ago in reply to kai klaas69

Intellectual 880 points

Dear Kai,

Thank you.

Christopher

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UAF42: Band Pass Filter