Subject: Re: Amplifying stage with *negative* Voltage gain??
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Date: Sun, 08 Dec 2002 15:07:55 -0500
NNTP-Posting-Date: Sun, 08 Dec 2002 15:08:00 EST
Organization: Bell Sympatico
Sorry if this has been suggested before but it is such long thread.
Is it frequency sensitive ?
Does the scope have a square wave output ?
If it does, do you have the same problem ?
If it doesn't , How does it behave with AC waveform ?
What about DC using a 1.5 battery ?
On Sat, 07 Dec 2002 13:10:38 -0800, Mike Monett
>Paul Burridge wrote:
>> On Fri, 06 Dec 2002 08:20:34 -0500, Mike Monett opined
>> >This was tony's suggestion. He is always right.
>> I'll bear that in mind in future. :-)
>> >I can't figure out what you mean by "2.2 tenths of a volt".
>> When using the 10X setting on the probe and the scope set on
>> 0.1v/div., the p-p waveform occupies just over 2 divisions. I guess
>> that equates to 2.2v?
>Yes, you are correct.
>> >If you are taking p-p measurements from the scope, you need to account
>> >for the trace width and the fuzz caused by scope noise.
>> SFAICS, these are both negligible WRT the signal.
>You have a very fine scope! The fuzz appears on higher bandwidth scopes
>due to noise at the input stage.
>> What I *cannot* understand is why on the x1 probe, Vin is four times
>> larger than Vout., whereas with X10., the signal levels are almost the
>> same. It's a heck of a discrepancy. Can anyone enlighten me?
>When the probe is set to X10, there is a 9 megohm resistor in parallel
>with a small cap at the probe tip. This provides minimum loading to the
>When the probe is set to X1, the resistor and cap are shorted. The probe
>cable and input capacity of the scope now appear at the probe tip. This
>loads the circuit, and is what Tony referred to.
>The effect this has on the signal depends on the source impedance and
>In the case of the emitter follower, there are two different impedances.
>On the positive-going signal, the emitter follower is turned on and
>provides a low impedance. On the negative transition, the resistance in
>the emitter may not supply enough current to the load, and the transistor
>turns off. The output signal becomes distorted, and starts looking like
>the output of a half-wave rectifier driving a capacitor.
>I simulated this effect using load capacitances from 0pf to 400pf:
>There are 5 different waveforms superimposed. They represent the value of
>the cable and scope capacitance in 100pf steps. Do any of these waveforms
>resemble what you see on the scope?
>> BTW, your screen shots were very helpful. What simulation program do
>> you use?
>MicroCap V SPICE