# CN-0312 why not use ADG733 to replace ADG633

Hi support:

CN-0312 why not use ADG733 to replace ADG633?

For AD8615 circuit, the on resistance of ADG733 is smaller than ADG 633.

If use ADG 733,  the performance of circuit will get better?

It is only cost consideration?

For the LED driver, also use ADG633.

How large resistance and how large leakage current could I choose for this switch ?  50ohm, 100 ohm?

How to evaluate this resistance and leakage current ?

Or there are other more important considerations?

best regards

Parents
• Hi future,

CN0312 mentioned the reasons why it used both the ADG633 and ADG733. The ADG633 was used because of its very low leakage currents and low parasitic while the ADG733 is for its lower on resistance (compared to the ADG633) to have a very low % gain error.

See link for the comparison of performance below:

The CN0312 not only considers cost but also considers the performance of the switches respectively and how it affects the system.

You may evaluate the two switches by using the board and order at the CN0312 product page.

Also, for CNxxx related concerns, you may post your questions at the Reference Circuit Community found at Design Center tab. See below.

Let me know if this helps.

Regards,

May

• Hi May

For the attached LED driver circuit.

How to decide the resistance of R3,R12,R13.

If I want the LED current to change from 0mA to 100mA.

The maximum current of BJT is 100mA.

R12 is 3.3V/100mA=33 ohm ?

But How to design R3,R13 ?

This R3, R13 is ok for the entire current range 0mA to 100mA ?

Reply
• Hi May

For the attached LED driver circuit.

How to decide the resistance of R3,R12,R13.

If I want the LED current to change from 0mA to 100mA.

The maximum current of BJT is 100mA.

R12 is 3.3V/100mA=33 ohm ?

But How to design R3,R13 ?

This R3, R13 is ok for the entire current range 0mA to 100mA ?

Children