AD828AR unexpected output

Hi Lathoi ,

It is due to the output swing of the part, if you are powering from only +5V single supply then you will see output swing from around 1.5V to 3.5V at 500-Ohm load.

Best regards,

Gio

Hi Gio, 

Thank you for response,

But data sheet say

" The AD828 is fully specified for operation with a single 5 V
power supply and with dual supplies from ± 5 V to ± 15 V. This
power supply flexibility, coupled with a very low supply current
of 15 mA and excellent ac characteristics under all power supply
conditions, make the AD828 the ideal choice for many demand-
ing yet power-sensitive applications".

That means it should give minimum out put ( may be approx. <700mV)  with input grounded, is it not? But as per you out may go up to 3.5V without any input. My question not what is the out put swing for +5Vs operation, but why there is output with out any input?

Hi Lathoi ,

You're saying that without input your expected output is around 0V, that is true if you are using rail to rail amplifier. But the AD828 has 1.5V swing from both supply rails (0V +1.5V and 5V-1.5V) so it will swing around 1.5V from the expected 0V output. Apologies for not clarifying on my previous response but the 3.5V is a result of 1.5V swing from the +5V rail. 

if you want to achieve a 0V output without any input, I suggest to try using ±5V and observe what happens to the output, there you will see an output around 0.

Best regards,

Gio

Hi Lathoi ,

You're saying that without input your expected output is around 0V, that is true if you are using rail to rail amplifier. But the AD828 has 1.5V swing from both supply rails (0V +1.5V and 5V-1.5V) so it will swing around 1.5V from the expected 0V output. Apologies for not clarifying on my previous response but the 3.5V is a result of 1.5V swing from the +5V rail. 

if you want to achieve a 0V output without any input, I suggest to try using ±5V and observe what happens to the output, there you will see an output around 0.

Best regards,

Gio

I am looking for Not exactly 0V but max 0.35V without any input or input grounded. I need to add extra circuit for -5V generation. As per data sheet it say i can operate with single supply also.

Hi Lathoi ,

Yes you can use the part on single supply configuration but cannot produce 350mV output using single supply due to the output voltage swing of the part. Aside from max the .35V swing from the ground, can you share other specs that you need for your applications so I can recommend some parts from our portfolio? The solution is either you adjust your supply or use a rail to rail output part if you want to achieve this 350mV max output without any input/ input grounded.

Thanks,

Gio 

Thank you Gio for your time, Looking for same specification of AD828 with RRIO in single supply operation. Slew rate of min. 50.  I am planing to use AD8092.

Hi Lathoi ,

AD8092 is a good choice. Kindly let me know if you encounter any challenges.

Best regards,

Gio