2 Replies Latest reply on Aug 2, 2017 3:36 PM by seg

    PGA_Component

    m.trotta_1730276

      Hi everyone,

         

      is there a way to modify a PGA component to allow GAIN < 1 ?

         

      Kind regards

        • 1. Re: PGA_Component
          user_342122993

          Not really, you have to use external components

          • 2. Re: PGA_Component
            seg

            The PGA is made from an opamp, a resistor string, and a bunch of switches. In PSoC1, the top of the resistor string was switchable to the opamp output. Thus we could make a voltage follower followed by a resistive divider made from the tap. Cool, but it has its problems. The switch in series with the upper section of the tap can add as much as 0.7% non-linearity depending on absolute signal voltage and the 5.0 or 3.3 V power supply. This was a huge error for most customers, so in PSoC3, 5LP, and 4, the upper end of the tap is hard-wired to the opamp output. This gives better accuracy in PGA, but loses the divider that was often handy in PSoC1.