Low Noise, Low Distortion Single-Ended Input Drive Circuit for Differential Input IF Sampling ADCs
The ADL5535/ADL5536 is a high linearity (third order output intercept, OIP3 = +45 dBm at 190 MHz), single-ended, fixed gain amplifier that can be used as a driver for high performance IF sampling of analog-to-digital converters. The ADL5535 has a gain of 16 dB and provides a simple approach to raise the signal from approximately 400 mV p-p to the 2 V p-p full-scale level required by the ADC. The ADL5535 low noise figure (3.2 dB at 190 MHz) and low distortion ensure that the ADC performance is not compromised. The ADL5536 can be used where a gain of 20 dB is required.
Figure 1. Schematic of the ADL5535 Driving the AD9268 16-Bit ADC, (Simplified Schematic: All Connections and Decoupling Not Shown)
Figure 2. Normalized Frequency Response of the ADC Interface Shown in Figure 1
The single-tone performance for an input frequency of 170 MHz and a sampling rate of 122.88 MSPS is shown in Figure 3. Two-tone performance is shown in Figure 4.
Figure 3. Measured Single-Tone Performance of the Circuit Shown in Figure 1 for an Input Frequency of 17 0MHz and Sampling Frequency of 122.88 MSPS
Figure 4. Measured Two-Tone Performance of the Circuit Shown in Figure 1 for Input Tones Centered at 170 MHz and a Sampling Rate of 122.88 MSPS