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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Buffer questions using 40106
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Dr. K



Joined: Jan 15, 2020
Posts: 27
Location: wisconsin

PostPosted: Sat Jun 20, 2020 3:25 pm    Post subject: Buffer questions using 40106 Reply with quote  Mark this post and the followings unread

Hi Folks, I've been boxing up several noise-making devices, but am finally starting my Lunetta project in earnest. The plan is to start with several basic oscillators. I've been consulting Hackaday for a lot of the mechanics.

I'm going to be using some 556's, so I can have voltage controlled oscillators. I'm also going to use 40106s to make several generic square and triangle wave oscillators.

Hackaday is using the INPUT side of the 40106 for triangle wave generation. I thought that was clever. What I just learned (and it explains why I haven't been able to amplify the triangle output) is that the amp and the oscillator, aparently, are talking to each other. They are using a 4069 as a buffer stage. A unity gain stage. I don't have any 4069s, but I do have LM324s. I don't fully understand what's going on--but any op amp set up as a unity gain should work, shouldn't it? To give credit where it's due, the image came from here. https://hackaday.com/2015/03/09/logic-noise-sawing-away-with-analog-waveforms/
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blue hell
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Joined: Apr 03, 2004
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Location: The Netherlands, Enschede
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PostPosted: Sat Jun 20, 2020 3:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, the usual (non-inverting) unity gain opamp circuit should do it.
_________________
Jan
also .. could someone please turn down the thermostat a bit.
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Dr. K



Joined: Jan 15, 2020
Posts: 27
Location: wisconsin

PostPosted: Sat Jun 20, 2020 4:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Yes, the usual (non-inverting) unity gain opamp circuit should do it.


That sounds good. Does it seem like a good strategy? Use the 40106, and take 3 oscillators for square waves and 3 as triangle waves with op-amp buffers? I can't imagine their would be a downside to using a buffer, that you would ever want the un-buffered output.

It's been a fun project, but the learning curve has been rough!
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Steveg



Joined: Apr 23, 2015
Posts: 182
Location: Perth, Australia

PostPosted: Sat Jun 20, 2020 7:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Dr K.

A simple emitter follower transistor will do the job. For example: https://www.electronics-notes.com/articles/analogue_circuits/transistor/transistor-common-collector-emitter-follower.php
If the output is direct to the output amp / mixer then you can replace the emitter resistor with a pot and take the output from the wiper and you have a built in volume control.

Steveg
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Dr. K



Joined: Jan 15, 2020
Posts: 27
Location: wisconsin

PostPosted: Sun Jun 21, 2020 3:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Steveg wrote:
Hi Dr K.

A simple emitter follower transistor will do the job. For example: https://www.electronics-notes.com/articles/analogue_circuits/transistor/transistor-common-collector-emitter-follower.php
If the output is direct to the output amp / mixer then you can replace the emitter resistor with a pot and take the output from the wiper and you have a built in volume control.

Steveg


Great! Thanks, that's a cheaper and simpler solution. I'll be bread boarding things before soldering them up. I'm just new enough to this, I wasn't sure where to start. It's annoying--when you wire something "correctly", yet can't get it to work. Diagnosing a problem, when it's actually a total mystery how it works, is hard! I have a pretty good stash of transistors and chips.
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Dr. K



Joined: Jan 15, 2020
Posts: 27
Location: wisconsin

PostPosted: Sun Jun 21, 2020 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Steveg wrote:
Hi Dr K.

A simple emitter follower transistor will do the job. For example: https://www.electronics-notes.com/articles/analogue_circuits/transistor/transistor-common-collector-emitter-follower.php
If the output is direct to the output amp / mixer then you can replace the emitter resistor with a pot and take the output from the wiper and you have a built in volume control.

Steveg


I think I misunderstood--you'd configure it like this image--with a square wave input to a transistor, then using an RC circuit, convert the square wave to a (more or less) triangle wave.


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Steveg



Joined: Apr 23, 2015
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Location: Perth, Australia

PostPosted: Sun Jun 21, 2020 8:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you just want a buffer you would leave the capacitor out and you would get an output waveform identical to the input.
Adding the capacitor in gives the decaying edge which might be something interesting for a drone box.

BTW if you are following Elliot Williams series on Hackaday, you might be interested that he posted here as hexagon5un.
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dk



Joined: Feb 12, 2019
Posts: 115
Location: Europe

PostPosted: Tue Jun 23, 2020 6:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Just a quick note... the triangle out will be lower in volume than the square. The triangle stretches in voltage only to where the 40106 flips, ie the lowest point of your triangle will be ~1/3rd of the supply voltage and the highest ~2/3rds. If you want the triangle to be at the same output level, you'll need a bit of amplification, not just a buffer.
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Steveg



Joined: Apr 23, 2015
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Location: Perth, Australia

PostPosted: Wed Jun 24, 2020 6:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Even amplifying the triangle wave to full peak voltage it is still going to be lower volume than the square wave (it has less area under the curve). Because you want the square wave at full volume for logic operations most people seem to ignore the difference and compensate for it in the mixer settings.
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dk



Joined: Feb 12, 2019
Posts: 115
Location: Europe

PostPosted: Thu Jun 25, 2020 4:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, sorry, I should have phrased that differently. If you want at least a somewhat similar peak to peak voltage, you'd need to amplify the triangle. I.ve amplified mine as I'm personally trying to make sure the output of any given module can be run into the input of any given module and have it still "work" (CMOS doesn't like non-square/pulse inputs, so "work" is subjective). If you'll use it solely for audio or don't mind the limited swing, a buffer is fine.
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