Rbe over temperature?

[Grant Richter]

Sorry, I thought you meant delta Vbe or the voltage difference between the
Base Emitter junctions of the two transistors for a given temperature.
Typical matching specs call for less than two millivolts difference, but
MATs and LM394 talk about microvolts difference.

So as long as delta Vbe remains constant over temperature it should not
affect the scale factor?

> From: "Ian Fritz" <ijfritz at earthlink.net>
> Reply-To: owner-synth-diy at node12b53.a2000.nl
> Date: Mon, 15 Jan 2001 11:31:17 -0700
> To: <grichter at asapnet.net>, "Terry Michaels" <104065.2340 at compuserve.com>,
> "synth" <synth-diy at node12b53.a2000.nl>
> Subject: Re: Rbe over temperature?
> 
> Grant --
> 
> Sorry, I don't understand your question. dVbe is the differential input
> voltage to the converter. The output current is I ~ exp(-dVbe/(kT/q)). So at
> the pitch corresponding to dVbe=0 there is no T dependence.  As the input
> control voltage increases from this point dVbe becomes negative and the
> pitch increases. The higher the pitch, the larger the temperature effect.
> Similarily for decreasing control voltage (dVbe is positive, with more
> temperature effect the lower the pitch.)
> 
> Hope this helps.
> 
> Ian
> 
> 
> ----- Original Message -----
> From: "Grant Richter" <grichter at asapnet.net>
> To: <ijfritz at earthlink.net>; "Terry Michaels" <104065.2340 at compuserve.com>;
> "synth" <synth-diy at node12b53.a2000.nl>
> Sent: Monday, January 15, 2001 11:15 AM
> Subject: Re: Rbe over temperature?
> 
> 
>> The design uses an SSM2220, which is basically an F grade MAT-03.
>> 
>> How much dVbe mis-match is tolerable?
> 
> 
> 
>