Diodes for the Bandido II uMax

[Ulf]

Hello

I am worrinig a little bit about the diodes in the schematic of the bandido II uMax. I would recommend Schottky Diodes especially for the voltageinverter for the neg. supply. Only in the feedback of IC10 i'm not shure what to use. In the schematic they are named as D7a, D7b respective D8a and D8b. Is it essential to use paired diodes and what type of diodes are recommended at that place. The outputvoltage swing of IC10 is directly affected by the forward voltage of the used diodes.
The adjustable "reference-voltage" of the following comparator (IC is so small, that the the outputvoltage swing with Schottkys in the feedback would be sufficient. Am I right so far ?

Thanks for any tips.

Ulf

[Mike]

Still not sure

Hi Ulf,

I can't say I have an extensive knowledge of electronics, but since nobody else has posted yet, I thought I'd say something.

The question is, why are the diodes there in the first place? Is it because they are used as part of the metal detection process, or are they there to stop the op-amp saturating which would lead to a slow recovery from a strong signal? I suggest the first would use Schottky Diodes, the second silicon to ensure best sensitivity. I suspect the reason for the diodes is the second case, and hence silicon diodes are used. But this is just a guess.

This question could be easily answered if someone with Bandido/Silver Sabre could measure the forward voltage of D7 and D8 (and the negative supply diodes).

Mike

[Unregistered]

Hi Mike

I also think that the diodes are for limiting the voltage swing. Right now i have used the schottky dioes everywhere and it is working. But as you wrote in your headline "I'm still not sure" ;-) if it works optimal.
Let's wait for somebody will be so kind to measure the forwardvoltage of a bought bandido.

Ulf

[Unregistered]

Abouth diode

Hi
I compare diagram of BANDITO II uMAX with other TESORO shematics and Fisher diagrams.You can use Shotky diode or 1N4148 diode(like as some original Tesoro shematics).
In some shematic D8a and D7b missing !!!This shematic can work like LOG AMP ( have big dinamic range (when have or miss metal target under coil) in the output of reciver) I the moment I do test with this shematic but waiting PCB from factory and not finish board to start real test.