ADG904: How can a dc bias be aplied to RF input.

ADG904 AN: AN-952: ADG9xx Wideband CMOS Switches: Frequently Asked Questions | Analog Devices How can a dc bias be applied to RF inputs? To minimize any current drain through the termination resistance on the input side, it is best to add the bias on the output (RFC) side. This is the best practice, especially for low power portable applications, but it may be necessary to apply dc-blocking capacitors on the RF outputs if downstream circuitry cannot handle this dc bias. Can a higher dc bias than 0.5 V be used? Figure 1 shows (AN-952 page.2) that the on resistance increases exponentially as the input signal increases. It also shows that a dc signal higher than 0.5 V (Figure 1) contributes to loss across the switch and the user will want to keep the on resistance to a minimum. As with standard CMOS switches the signal applied to the switch inputs should never exceed the V DD supply. If you look at Figure 1 (AN-952 page.2), from the link above, you can see that the Ron changes as the voltage increases. So it’s best to apply a 0.5V Bias, This is all explained in the app notes.

Question: How can a DC bias be properly applied to the RF input of a device? Answer: To reduce input current drain, apply bias on the output (RFC) side—ideal for low-power designs. Use DC-blocking capacitors on RF outputs if downstream circuits can't handle the bias.

ADG904: input power and -1dB compression

Question Our signal is 70MHz 5dBm. The input power for ADG904 is 7dBm (0V dc bias), 16dBm (0.5V dc bias), the -1dB compression point is 16dBm. It seems the-1dB compression point is larger than input power which is -3dB point normally.Can you please explain the conflict between the input power and -1dB compression point?When you test the -1dB compression point, is there any dc bias? Answer P1dB is measured with a 0dBm low level input signal (no DC bias) and the power is increased until your signal loss is down by 1dB.The 7dBm nominal i/p power is the signal the switch can handle without being clipped.Please see attached note for details.