SLOS930C November 2015 – October 2024 THS4541-Q1
PRODUCTION DATA
Operating the THS4541-Q1 with a DC-coupled differential input source is very simple and only requires that the input pins stay in range of the DC common-mode operating voltage. One example is a DC-to-50-MHz quadrature down-converter output. These outputs typically sit on a DC level with some internal source impedance to the external loads. The example of Figure 8-5 shows a design using the THS4541-Q1 with a simple, passive RLC filter to the inputs (the Rg elements act as the differential termination for the filter design). From the original source behind the internal 250-Ω outputs, this circuit is a gain of 1 to the THS4541-Q1 output pins. The DC common-mode operating voltage level shifts from the 1.2-V internal, to the mixer, to an output at the ADC Vcm voltage of 0.95 V. In this case, a simple average of the two DC voltages in the gain of 1 stage gives a 1.08-V input pin common-mode result that is well within range.