A variable gain CMOS amplifier with exponential gain control

Study of Small-signal Model of Simple CMOS Amplifier with Instability Compensation of Positive Feedback Loop

“…An example in [28] allows similar type of gain control (gain ≥ 1) as the circuit proposed in this paper. The range of gain adjusting is even higher (35 dB) than in our case.…”

“…Based on this comparison, we concluded the following advantages of our solution: proposed circuit uses very low number of transistors, has low power consumption (in comparison to adjustable structures [18][19][20][21][22][23], [28]), does not require additional bias source(s) as [18][19][20][21][22][23][24][25], [27], [28] and internal conception is not based on typical differential pair approaches [18][19][20], [22], [23], [28], [29]. We found examples of circuits that combine lower power consumption [24][25][26][27], [29] and lower number of transistors [25][26][27] than our proposal.…”

“…We also studied several hitherto published solutions [18][19][20][21][22][23][24][25][26][27][28][29] of the VGAs and simple CMOS amplifiers. The main attributes of these solutions are focused on wide-range gain control (± 40 dB) and they usually require many bias sources ( [18], [19], [22], [23], for example).…”

“…The main attributes of these solutions are focused on wide-range gain control (± 40 dB) and they usually require many bias sources ( [18], [19], [22], [23], for example). Many of the known structures are based on specific utilizations of the differential (transconductance) sections [18][19][20][21][22][23], [28], [29] but some circuits also operate without a differential section [24][25][26][27]. Moreover, many of the previously introduced structures use biasing current sources not only for biasing of the transconductance sections, for example [24], [25], [27].…”

“…Moreover, many of the previously introduced structures use biasing current sources not only for biasing of the transconductance sections, for example [24], [25], [27]. The bias source of the transconductance section [18][19][20][21][22][23], [28], [29] is necessary for g m adjusting. Of course, it causes changes of the DC current from the supply source and therefore if gain is rising, power consumption increases substantially.…”