Digital Gain Control: R-2R Ladder
{"Image DocumentName": "Digital Gain Control: R-2R Ladder", "Image ImageDescription": "Sj1. Sj3. Sj4. Sj5. Sj2. Sj0. S(j-1)0. I1. VOUT. R. 2R. S00. Sn0. Sj0. S10. Mixer Current. I1. VDD. When Sjk=1, DGjk=-6 j+20LOG(1+k/6) (dB) The mixer load resistor is designed as a 10 section R-2R ladder. By switching the mixer output current to various node in the R-2R network, the output voltage signal (VOUT) varies in the power of 2, realizing 6dB/step gain control. Each R in the network can be further split into 6 equal parts and achieve finer gain variation at roughly 1dB/step, as indicated in the formula and the transfer curve. Note that the R-2R ladder guarantees monotonic gain control. It is highly linear, settles fast and maintains constant output impedance. Mixer resistive load: 10-section R-2R ladder. Monotonic, linear, fast settling and Constant Rout. 3/18/2004.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}