TS1001 low power, low voltage op-amp review

in Chips, part review by SQKYbeaver | 3 comments

We have been experimenting with the Touchstone semi TS1001 ultra-low power, low voltage op-amp demo board, and the results are in.

For our tests, the board inverting op-amp circuit was powered by a solar cell from a calculator with two 0.5v zener in series. The total supply was about 950mV, well below the operating range of most op-amps. It consumes 1.3 micro watts when the input is driven by an 1Khz 500mV square wave.

From our initial testing we found a usable bandwidth of about 1KHz, this op-amp appears best suited for low power sensors. Replicating a sine wave (blue signal) up to about 850hz is possible, any further and you end up with a more triangular wave as shown above (yellow signal).

Keep reading for more before and after signal comparisons.

 

This first capture shows that there is an input(yellow) offset of about +160mV.

This capture shows the rise time is about 460uS, the falling times are similar to the rising time.

Zooming in an 20uS delay can be seen above.

Replicating a sine wave up to about 850hz is possible(above) ,any further and you end up with a more triangular wave.(bottom)

Overall the TS1001 is suited for low speed sensor applications where the voltage being input is fairly stable and not expected to have a full-scale change in less than 500 micro seconds.

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Comments

  1. April says:

    Good research DP. Got here through 43oh.

  2. ultrasounder says:

    Looking at the scope captures 4 and 5 is not clear to me if there is a phase reversal, the thing that you allude to as the 20uS delay. The datasheet claims that there is no phase reversal at 0.65V supply. Very nice work!.Thanks.

  3. Jeroen Fonderie says:

    Hi ultrasounder:
    It may be helpful if I try to explain what we mean when we talk about phase reversal in the TS1001 data sheet. Back when most opamps were still made in bipolar technologies, phase reversal was a common but undesired phenomenon. If you drive the inputs of a bipolar opamp beyond the limits of its common-mode input range, you end up saturating the input transistors and this may cause current to flow from the base to the collector, in the opposite direction from what was intended. So the signal current reverses direction and that in turn causes a sudden reversal of the output voltage. If you Google “opamp phase reversal scope shot” and look at images, you will see a very telling example as the first entry.
    In a good opamp design, be it in bipolar, JFET or CMOS technologies, this reversal is prevented from happening and that is exactly what we did in the TS1001. And rightfully so, because if your supply voltage is just 0.8V, it doesn’t take that much to accidentally drive the inputs beyond the supply rails.
    What is shown in the scope shots above, is the effect of phase delay, rather than phase reversal; the opamp has a small-signal bandwidth of about 4kHz, so when you get closer to this unity-gain frequency, there will be a delay between the input and output signals.
    Hope this helps,
    Jeroen Fonderie
    VP Engineering, Touchstone Semiconductor

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