Instrument input design questions

I'd like to build an instrument input for the front end of a micamp. While i've FINALLY started to understand how a transister (bjt) works from a purely theoretical and not very scientific point of view, I still know essentially nothing with regard to applying that theoretical knowledge.

My GOAL then would be to design a discrete impedance buffer/phase splitter, considering the following;
    1. My intended load would be an amp based on the INA217 and the circuit recomendation found in it's datasheet.

    2. I considered using an op-amp as a buffer, however given the differential input of the 217 unless i used a dual op-amp i would still only have one input signal.

    3. Using an op-amp wouldn't teach me what i want to know.

    4. I need a high impedance input (1M?) and a Low impedance (200ohm) Differential output.


This leads to a whole lot of questions.....


First, would this benefit more from using a BJT or an FET? I read in TAOLE pp.86 that as a current amplifying device, BJT's have a low input impedance and a high output impedance. Is that based on configuration, as in common base?

I found this in the same book, pp. 97 Figure 6.33:


*notated that the Ic will only differ from Ie by the loss of the base current. I can live with that. Can someone nudge me in the right direction here?

This almost reads incomplete. Here is the rest of my incomplete thought.
    If (we) were to pick some small signal device to base calculations on:
Other than strapping a R to the input (Big R, noise?), is there an elegant way to set the in/impedance to satisfy my bridging needs?

To be clear, I don't want someone to design this for me. I realize there are a million buffer circuits out there, my thoughts were more along the lines of learn by design. So if a device were chosen, perhaps someone could walk me through the math as i'm still trying to understand component correlation in circuit.

Plagiarize more.

What PRR said.

Most of the time, when people build solid-state instrument preamps, they use FETs rather than BJTs. Use a FET voltage amplifier to drive a DI-intended transformer (Jensen makes a very nice one), figure out a power supply and you're there.

Peace,
Paul

...and that reminded me of one other curiosity. A transister can be configured as a voltage or current amplifier; what would be the benefit of using one over the other in an amp circuit??...impedance for one?? Go ahead and shoot me.
Ben.

plagiarize more  : I'm not wholly sure if that was meant as sand in my face. However, as the resident guru i ALWAYS welcome your valuable input.

Paul, i had intended to cap couple the inputs on the micamp so i was trying to avoid a TX. Again, thank you for the input. (no pun)
Ben.

Maybe use a pnp, should have slightly better noise. A BC560 or similar.

> meant as sand in my face

No. Perhaps it would be more polite to call it "research". But studying how others did it IS an excellent way to learn.

Your first drawing is so incomplete that I thought you had a LOT to learn. You can learn by studying other plans, which is easier for me than typing a long-winded free lesson.

Your second drawing points out the possibility that a PNP may be less hissy than NPN, but there is an un-mentioned change which is much more important. (Still incomplete.)

And.... go back to your REAL issue. You have a gitar you want to record. Why balance it into a mike hole which will usually just unbalance it again? Bal/unbal aside, what ARE your voltage and current needs? How much voltage and current can the gitar do? How much voltage and current does a mike amp need? How much V and I to go into a Line Input?