TS321: block diagram

Toshiro Imi

Part Number: TS321
Other Parts Discussed in Thread: LM2902, LM2904

Hello

While I have checked TS321 block diagram, i realized that the output low side PNP was E-B short circuit, and I think this is malfunctional. Since I have put the block diagram on here, please check it and show me the correct one.

TS321 block diagram.pdf

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 270560 points

Yes, the base connection is drawn wrong and must go further to the left (Q13/Q12 in the ST datasheet).

0 kai klaas69 over 1 year ago

Guru 140200 points

Hi Toshiro,

since the TS321 is a clone from the ST's original TS321, I think the original datasheet of TS321 shows a correct block diagram.

By the way, there's more wrong: The transistor with the compensation cap at the base should be a PNP, not a NPN. A NPN would degrade the performance of the current mirror of the input stage.

Kai

0 Ron Michallick over 1 year ago in reply to kai klaas69

TI__Guru*** 145736 points

0 Toshiro Imi over 1 year ago in reply to Ron Michallick

TI__Expert 6460 points

Hi Ron,

Thank you very much for sharing the correct block diagram.

One another question : Could you tell me why sink current source is connected across OUT and GND.

The reason of this question is that our customer found the performance difference between TI's TS321 and ST's TS321 when he applied the input common mode voltage exceeded VCC-1.5V of the spec. TI's TS321 keeps low state but ST's TS321 does not. I am thinking that TI's TS321 keeps OUT Low state by this sink current source.

Best regards,

+1 Ron Michallick over 1 year ago in reply to Toshiro Imi

TI__Guru*** 145736 points

Toshiro,

The sink current source is connected across OUT and GND to allow VOL to come close to 0V. The PNP output cannot conduct until output is about 0.6V ; ST should also have this current sink. Many decades ago when TS321, LM2902 and LM2904 were new , VOUT near zero was a rare thing.

It is important that at least one input is low enough (in valid common mode range) to keep input stage biased.

This application note highlights things that make TS321 unlike most other modern op amps.

Design Guidelines for Devices with LM324/LM358 Cores

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TS321: block diagram