Flag Counter
Since 08.08.2014
Counts only, if "DNT = disabled".

Your IP is
Valid HTML 4.01 Transitional Creative Commons Lizenzvertrag
We love the King
23. July 2024
Your valuable opinion :
4.5 stars

Avg. 4.87 from 23 votes.

Logarithmic_Amplifier_AD8307.php    6675 Bytes    23-04-2024 10:59:14

Logarithmic Amplifier with the AD8307

Thank You Analog Devices for this nifty chip !

•  few kHz to more than 400 MHz
•  -60 dBm ... +10 dBm >> +3V ... +10V, 1V/10dB

Logarithmic Amplifier with AD8307

✈ Circuit Description

Logarithmic Amplifier with AD8307

The RF is directly coupled to the AD8307 via R1 and C1. The output of the AD8307, usually 25mV/dB is pulled down to 20mV/dB with R4 and R5. The signal is then amplified by an OP07 with an amplification factor of 5. Therefore you'll get an output of 100 mV/dB or 1 V/10 dB of RF-Power. The slope of the log-amp is adjusted by R7.

✈ The Workhorse : AD 8307

Logarithmic Amplifier with AD8307

"The AD8307 is the first logarithmic amplifier made available in an 8-lead SOIC_N package. It is a complete 500 MHz monolithic demodulating logarithmic amplifier based on the progressive compression (successive detection) technique, providing a dynamic range of 92 dB to ±3 dB law conformance and 88 dB to a tight ±1 dB error bound at all frequencies up to 100 MHz. The AD8307 is extremely stable and easy to use, requiring no significant external components. A single-supply voltage of 2.7 V to 5.5 V at 7.5 mA is needed. A fast acting CMOScompatible control pin can disable the AD8307 to a standby current of 150 µA." says the datasheet.

✈ Calibration

In order to calibrate this thing, we suggest the following setup. It does produce a squarewave (am) modulated signal with -30 dBm / -70 dBm.

Logarithmic Amplifier with AD8307

Use R4 (50kΩ) to adjust for 4 Vpp, representing the 40 dB difference. Then adjust for the absolute value with R7 (50kΩ).

Logarithmic Amplifier with AD8307

✈ Frequency Response

Logarithmic Amplifier with AD8307

Knowing the Frequency Response enhances the range of usability.
Vertical : Volt, Horizontal: MHz. Blue: 0 dBm, Red: -20dBm. Yes, we calibrated at 100 MHz.

✈ Downloads

✈ Share your thoughts

The webmaster does not read these comments regularely. Urgent questions should be send via email. Ads or links to completely uncorrelated things will be removed.

Your Browser says that you allow tracking. Mayst we suggest that you check that DNT thing ?

t1 = 6585 d

t2 = 272 ms

★ ★ ★  Copyright © 2006 - 2024 by  ★ ★ ★