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DIY Stompboxes => Building your own stompbox => Topic started by: coxter on August 24, 2006, 05:44:21 AM

Title: TL072 Opamp help
Post by: coxter on August 24, 2006, 05:44:21 AM
Hi, I'm really new to this so I just need a little guidience,

What does pin 4 and 8 do? I dont understand what Vcc means...
Thank you

(http://i87.photobucket.com/albums/k159/noobz4ever/TL072.gif)
Title: Re: TL072 Opamp help
Post by: Mihkel on August 24, 2006, 06:01:34 AM
Pin 4 should be ground
Pin 8 should be the positive power supply connection.
Title: Re: TL072 Opamp help
Post by: GibsonGM on August 24, 2006, 08:38:48 AM
How come pin 1 is listed as "offset null"? I didn't think the 72 had that available...am I high, isn't pin 1 just Output 1?? Hmmm.
Title: Re: TL072 Opamp help
Post by: Paul Perry (Frostwave) on August 24, 2006, 08:45:28 AM
GibsonGM, someone owes you a brew :icon_wink:
Title: Re: TL072 Opamp help
Post by: Paul Marossy on August 24, 2006, 10:18:36 AM
QuoteGibsonGM, someone owes you a brew

+1  :icon_cool:
Title: Re: TL072 Opamp help
Post by: redeffect on August 24, 2006, 10:24:59 AM
Welcome to the wonderful world of misprinted information.
Title: Re: TL072 Opamp help
Post by: coxter on August 26, 2006, 02:29:24 AM
Oh yes, thank you all very much for the clarification. So is this the top view of the chip or the bottom (with the pins pointing at me) view?


Quote from: coxter on August 24, 2006, 05:44:21 AM
Hi, I'm really new to this so I just need a little guidience,

What does pin 4 and 8 do? I dont understand what Vcc means...
Thank you

(http://i87.photobucket.com/albums/k159/noobz4ever/TL072.gif)
Title: Re: TL072 Opamp help
Post by: Mihkel on August 26, 2006, 05:57:45 AM
Top view, pins pointing down.
Title: Re: TL072 Opamp help
Post by: markm on August 26, 2006, 11:31:01 AM
Quote from: redeffect on August 24, 2006, 10:24:59 AM
Welcome to the wonderful world of misprinted information.

I thought I was the only one that used misprinted datasheets  :icon_mad:
Title: Re: TL072 Opamp help
Post by: ashcat_lt on August 26, 2006, 09:27:22 PM
Quote from: Mihkel on August 24, 2006, 06:01:34 AM
Pin 4 should be ground
Pin 8 should be the positive power supply connection.

is that the "bias voltage" or something else?  In other words, how does this compare to a 3 pin transistor, or not at all?
Title: Re: TL072 Opamp help
Post by: R.G. on August 26, 2006, 09:31:13 PM
Quoteis that the "bias voltage" or something else?  In other words, how does this compare to a 3 pin transistor, or not at all?
Almost not at all.

An operational amplifier is an entire circuit inside, all on its own. A transistor has to have external things to make it do much.

The +vcc and ground pins are where the DC power is supplied to make things go. No power on the power pins = no go.

The input is where you place input and feedback signals, and the output is where signal comes out of for use and for feedback.

In opamps, "bias voltage" is the voltage where you tie the + input. This sets the DC voltage level on the output and - input by the feedback operation of the circuit.
Title: Re: TL072 Opamp help
Post by: ashcat_lt on August 26, 2006, 09:46:38 PM
the reason I asked was that I think I've seen people recomend using this opamp (or half of it) in this circuit (http://www.muzique.com/lab/buffers.htm) for Q1.  Q1 only has 3 leads...???
Title: Re: TL072 Opamp help
Post by: ashcat_lt on August 28, 2006, 02:18:02 PM
Is this question just too silly?  Anybody got a link to "op amp basics" or something along that line?
Title: Re: TL072 Opamp help
Post by: Stompin Tom on August 28, 2006, 02:44:10 PM
God knows I ain't no expert, but doesn't that schematic on the datasheet (not in the above illustration) tell you what's going on inside the opamp? Anywho, if you look further down the AMZ buffer page you linked to, there's an opamp based buffer. Is that what you're refering to?

This datasheet, by the way, has the right pinout:

focus.ti.com/lit/ds/symlink/tl072.pdf