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THS3001: About THS3001

Part Number: THS3001
Other Parts Discussed in Thread: THS3491

Hi, support team

My customer has the questions as follow:

I want to use THS3001 with single supply and output high voltage.
But it didn't work.
The gain is 2, using evaluation board.

Could you recommend a single supply chip similar to THS3001? (output voltage max 25V, high BW)

Thanks so much.

Best regards,
Yuki

  • Hi Yuki,

    can you say why it didn't work? What is not working?

    Have you noticed that the THS3001 is no input rail to rail OPAmp and that the input voltage must stay 2V away from the supply voltages?

    Very most of the HF OPAmps being able to be supplied with a supply voltage of >25V are not input rail to rail. See for yourself:

    https://www.ti.com/amplifier-circuit/op-amps/high-speed/products.html#p1261max=25;44

    Please give more details on your application and post a schematic. What exactly is your input voltage?

    Kai

  • Use the much newer THS3491

  • Hi Michael,

    with the THS3491 the input would need to stay more than 4V away from the rails.

    Kai

  • Of course Kai, 

    when you are defining parts like this you have to ask the question if you really want to support unity gain buffer apps. Why? If so, your input signal has as much slew rate as the output but the THS3491 is intended to provide the gain to boost up both the amplitude and outpu slewing. 

    So, I intentionally gave the designer more leeway to cascode the input current source to improve CMRR (the input buffers for CFA have a relatively low CMRR as the gain is <1.0 - providing a higher impedance looking up and down towards the current mirror bias setups helps that). 

    So, yes the THS3491 has a relatively high input headroom but run with some non-inverting gain or inverting and that is a don't care.

  • So Qi, 

    If you need the slew rate of a current feedback op amp, you will need to deal with the input/output headroom requirements. Single supply is fine as long as the I/O swings stay away from the clipping limits. There are no RR input CFA devices and only 1 RRout CFA device in the world. So parts like the THS3001 and THS3491 provide the speed, but the design needs to keep the swings away from the supply rails the specified amount. How are you doing that with your gain of 2 design?