High frequency/high dynamic range CMOS VGA

A Wideband CMOS Variable Gain Amplifier With an Exponential Gain Control

“…The control voltage generator converts an external control voltage signal to an internal control voltage signal . This is consistent with the theory illustrated in [25].…”

“…To achieve both a high bandwidth over several hundred megahertz and a wide dynamic range, the CMOS VGA cell based on a differential cascode structure with a resistor load [25], as shown in Fig. 1(d), has been reported.…”

An Inherently dB-linear All-CMOS Variable Gain Amplifier

“…(1)(2)(3)(4)(5)(6)(7)(8) have assumed that the input transistors operate in triode region and the other transistors operate in saturation region. In the real circuit design, however, as the control voltage increases, the input transistors will gradually enter saturation region and, eventually, the gain no longer depends on V DS .…”

“…Robust dB-linear gain control can be implemented by using a negative feedback control [7,8]. The feedback loop composed of exponential generator and the replica VGA cell produces a dB-linear gain control voltage according to the inverse exponential input voltage.…”

A 2 GHz CMOS dB-linear programmable-gain amplifier with 51 dB dynamic range

“…However, the maximum gain control range obtained in this way is limited within 30 dB. For an even larger gain range, parasitic bipolar transistors can be used for accurate exponential transformation [5]. It has also been attempted to develop a PGA for a large dynamic gain range with linear-in-dB gain variation simply in a CMOS technology, several cascaded PGA stages have been used [6].…”