Overview: Detector Log Video Amplifiers (DLVA)
The content of this specification may change without notification7/01/09 DLVA
Detector Log Video Amplifiers (DLVA)
There are three basic types of logarithmic amplifiers, Detector-Log Video Amplifiers (DLVAs) Successive Detection Logarithmic Amplifiers True Log Amplifiers (TLAs) A detector log video amplifier (DLVA) is a type of logarithmic amplifier in which the envelope of the input RF signal is detected by a standard "linear" diode detector. The output of the detector is pressed in the video amplifier section, making input/output relationship similar to a logarithmic conversion. In general, the DLVA offers the advantage of operating over the widest frequency range, but at the sacrifice of dynamic range. Limited by the detecting range of square law of the input diode detector, typical dynamic range for a DLVA is approximately 40 dB. In quite a lot of usages, two log cascades are put in parallel with a RF amplifier incorporated in time of detection of the log cascade, so that the dynamic range can be extended to approx.70dB. The detected video sections of a DLVA can either be AC coupled, DC coupled, or pseudo DC coupled. Each has its advantages, depending upon the application (i.e., CW operation, temperature pensation, etc.). The basic configuration of a DLVA is simply a detector diode to convert the RF energy into a DC voltage followed by a video amplifier with a logarithmic transfer function. The bination results in a device which presses a large RF signal range into a narrow range of video voltage. We have put considerable effort into designing a DC coupled DLVA with very low baseline drift. Employing a tunnel diode based detector circuit .. coupled with a very stable DLVA, high-speed miniature DC DLVA with good recovery characteristics is available.
