No global feedback V TO I converter THD: < 0.001%

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sonnya

sonnya

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Joined 2001
mirand-audio.dk/?post_type=product
Hi all.

I could not sleep tonight.

I am in the process of doing a frontend for driving my TSSA V1.7 in Balanced/bridged mode.

For this i have developed a front end which convert a given voltage to current with as low distortion as possible without the use of global feedback.

I ended up having less than 0.001% THD. Which i think i okay.

This low distortion we have in the enhanced diamond buffer but also in the currentmirror. The currentmirror normally lays around 0.025%

A note to the V/I converter:
The currentmirror is only that good if driving into a virtual GND node. In other words into an inverting opamp - discrete or chip solution.

Of course there is more to the circuit than shown here.

  • You need a good current generator with high PSRR and low drift
  • U1, U2, U3, U4 is a dual package to lower DC drift
  • The powersupply (+/-15VDC) should be a low noise high PSRR type

I hope your all like it.
 

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sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
manso said:
The cfp in drive front end will probably make distortion worse rather than better.
Click to expand...

Hi ... I have been offline for some days... Sorry.

No actually, the distortion falls of. Secondly it stabilizes the idle current in the diamond buffer.

The idle current ratio is then set by R12,R13 versus R14,R15.

In this case x5.6. There is a little loss so we end up with ~x5

Believe me the distortion is very low. Driving a 1K load 4Vp gives you below 0.001% without global feedback.
 
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