THS4222: THS4222 as a buffer, simulate using TINA

Senthilnathan Munisamy

Part Number: THS4222
Other Parts Discussed in Thread: THS3092, TINA-TI

Hello All,

I am trying to use THS4222 as a buffer for 40MHz and 48MHz signals. below is the circuit in TINA

When taking a transient response i could see a phase difference between the input and output signals. In addition to this if the i/p voltage is 0 to 1.8V the o/p seen is -0.01V to 1.81V (i.e 10mV stretch in the input signals). I went through the datasheet and i couldn't find anything related to this. Can't this opamp be used for G=1 for 40M and 48M signals. Please clarify the below

1. Why there is a phase shift with the input and output 2. Why there is a 1mV stretch in the signals.

Attached the transient response below

Thanks in advance

over 7 years ago

0 kai klaas69 over 7 years ago

Guru 140200 points

Hi Senthilnathan,

if you take a look at figure 17 of datasheet, you will notice that the THS4222 has an open loop gain of only 10dB at 40MHz. So, with a closed loop gain of 0dB you have only a loop gain of 10dB, which is not enough to make the OPAmp work perfect.

If you want to handle 40MHz with very high precision you need a faster OPAmp.

Kai

0 Senthilnathan Munisamy over 7 years ago in reply to kai klaas69

Prodigy 40 points

Hi Kai,

Thank you for the info. I took some time to check for other opamp which will help me.

THS3092 - www.ti.com/.../ths3092.pdf
Will the above opamp serve my need?. Buffer for 40MHz signal with 4.4V peak. Slew rate looks fine but not sure about the stability. Kindly help me through this.

Thanks.

0 kai klaas69 over 7 years ago in reply to Senthilnathan Munisamy

Guru 140200 points

Hi Senthilnathan,

I have simulated your circuit with TINA-TI. The THS3092 looks a bit better than the THS4222.

Kai

0 Senthilnathan Munisamy over 7 years ago in reply to kai klaas69

Prodigy 40 points

Hi Kai,

Thank you for your inputs.

Warm Regards.

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THS4222: THS4222 as a buffer, simulate using TINA