1. Home
  2. Electronics Design
  3. input impedance of THAT 1512 IC

input impedance of THAT 1512 IC

Hey all;

I've been reviewing the THAT 1512 data sheet

formatting link
and am trying to figure out what the input impedance would be for the circuits they've given.In Fig. 4 on p. 6 for instance, would the input impedance be

1K, or 1K||1K = 500 ohms, or 2K, or something else altogether? What would it be for the T bias configuration in Fig.5 on p. 7? They also use the expressions 'differential' and 'common mode' impedance. When desgning a mic pre, which of these should be my primary concern?

Thanks

Reply to
tempus fugit
Loading thread data ...

"tempus fugit"

** The differential impedance is 2 kohms - this is what a typical "balanced" mic sees.

God knows what mic you have.

** 2.4kohms.

The impedance is set just by the resistors that you supply - the IC itself has figures in the many megohms.

... Phil

Reply to
Phil Allison

be

Thanks Phil.

I have several mics, but the one I'm trying to work this pre with is an SM57. It's my understanding that it was originally designed to see a 600 ohm input Z. So the input Z is the sum of the 2 resistors then? Also, it's the differential, rather than the common mode input Z that I want to concern myself with (in terms of loading the mic and potentially HP filtering it with too low an input Z?)

If I may, how did you arrive at that figure?

itself

Yes I knew that - I was just having trouble seeing how to set the input Z with the resistors.

Thanks again Phil

Reply to
tempus fugit

be

Forgot to ask one other question in my last post - so if I were working on an existing design using this IC, I could simply measure the reisistance between pins 2 and 3 to get the differntial input resistance (I realize I wouldn't actually have the impedance this way)?

Thanks again

itself

Reply to
tempus fugit

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.