Sorry Lads, really dumb opamp question

[Martin Czech]

your description confuses me... had not much sleep ...
new girl friend ... 

;->

So I keep generall:

A unity gain follower does not need any resistor.
Signal in is "+".
Connect output to "-".

Works only if such strong feedback is allowed for the op amp 
you are using ("unity gain compensation").

Input resistors are used (and are recommended)
if you are not sure if any transient may hit the 
"+" or "-" input during operation.

Note: an input transient means difference voltage 
to one of the supplies, or a signal spike.
OTOH if the signal line does not move, but the supply
does (turn on, off, power down etc.)
this is also regarded as "input spike".
Voltage means potential difference, it has no absolute meaning.

Cause this could lead to zener breakdown and
thus junction/metal meltdown.
A series resistor before the input can 
limit the current in this case, so no permanent
damage.

So , if the amp serves as output buffer or input
buffer, this could be worth the few cent for resistors.
Or if the amp is steered by a circuit with independent
supply (remember voltage difference).

And: the theoretical total impedance at any input to ground (short all
sources and then compute parallel/series network) should be equal to
that of the other input, thus avoiding additional offset trouble in
precision operation.

Sorry for beeing academic.

m.c.

:::Date: Wed, 10 Jan 2001 09:45:30 +0000 (GMT)
:::From: Ken MacBeth <macbeth2600 at yahoo.co.uk>
:::Subject: Sorry Lads, really dumb opamp question
:::To: synth-diy at node12b53.a2000.nl
:::Content-Transfer-Encoding: 8bit
:::
:::Apologies in advance! For a while now, if I want a non
:::inverting buffer, I take a dual opamp wire a 10k input
:::resistor to the neg. input, take another 10k, connect
:::one end to the neg. input then connect the other end
:::to the output, this output I then connect this to
:::another 10k input resistor to the other opamp which
:::has a 10k feedback resistor. The output of this is a
:::non inverting buffer amp.
:::The question is, would this function happen if I made
:::a resistor free non inverting buffer out of one opamp?
:::anyone know? regards, Ken
:::
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