Circuit Note

CN-0187

Rev. 0| Page 3 of 7

Typical measured performance characteristics of the circuit are

presented in Figure 2 through Figure 5.

0.01

0.1

1

10

–25

–20

–15

–10

–5

0

5

10

15

INPUT (dBm)

450MHz

900MHz

1900MHz

2350MHz

2600MHz

Figure 2. Measured VRMS Output vs. Input Level (Log Scale), 450 MHz,

900 MHz, 1900 MHz, 2350 MHz, 2600 MHz, Supply +3.3 V

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0

0.2

0.4

0.6

0.8

1.0

INPUT (V rms)

450MHz

900MHz

1900MHz

2350MHz

2600MHz

Figure 3. Measured VRMS Output vs. Input Level (Linear Scale), 450 MHz,

900 MHz, 1900 MHz, 2350 MHz, 2600 MHz, Supply +3.3 V

0.01

0.1

1

10

–25

–20

–15

–10

–5

0

5

10

15

INPUT (dBm)

450MHz

900MHz

1900MHz

2350MHz

2600MHz

Figure 4. Measured PEAK Output vs. Input Level (Log Scale), 450 MHz,

900 MHz, 1900 MHz, 2350 MHz, 2600 MHz, Supply +3.3 V

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0

0.2

0.4

0.6

0.8

1.0

INPUT (V rms)

450MHz

900MHz

1900MHz

2350MHz

2600MHz

Figure 5. Measured PEAK Output vs. Input Level (Linear Scale), 450 MHz,

900 MHz, 1900 MHz, 2350 MHz, 2600 MHz, Supply +3.3 V

The turn-on time and pulse response is strongly influenced by

capacitor connected to the VRMS output. Figure 6 (taken from

the ADL5502 data sheet) shows a plot of the output response to

an RF pulse on the RFIN pin, with a 0.1 μF output filter

falling edge is particularly dependent on the output shunt

capacitance.

1ms/DIV

70mV rms

160mV rms

250mV rms

400mV rms RF INPUT

VRMS

PULSED RFIN

Figure 6. Output Response to Various RF Input Pulse Levels, Supply3 V,

900 MHz Frequency, Square-Domain Filter Open, Output Filter 0.1 μF

To improve the falling edge of the enable and pulse responses,

a resistor can be placed in parallel with the output shunt

capacitor. The added resistance helps to discharge the output

filter capacitor. Although this method reduces the power-off

time, the added load resistor also attenuates the output (see the

Output Drive Capability and Buffering section of the ADL5502

data sheet). Figure 7 (taken from the ADL5502 data sheet)

shows the improvement obtained by adding a parallel 1 kΩ

resistor.