Differential amplifier with improved gain‐accuracy and linearity

Abstract

SUMMARYA novel circuit design technique is presented which improves gain-accuracy and linearity in differential amplifiers. The technique employs negative impedance compensation and results demonstrate a significant performance improvement in precision, lowering sensitivity, and wide dynamic range. A theoretical underpinning is given together with the results of a demonstrator differential input/output amplifier with gain of 12 dB. The simulation results show that, with the novel method, both the gain-accuracy and linearity can be improved greatly. Especially, the linearity improvement in IMD can get to more than 23 dB with a required gain.

Design of RF amplifier with enhanced performance

“…The proposed linearization technique, similar to [11,12], neutralises the distortion current caused by the feedback loop at the input of the amplifier, as a result the gain and PAE can be improved in addition to linearization.…”

“…Because of its unique I-V transfer characteristics, it can be realized as negative impedance when biased properly. Thus the NDR element can be used to replace the auxiliary amplifier in [11,12] to carry out the nonlinearity compensation in a RF feedback amplifier. In the novel linearization technique, using the NDR can cancel the additional power dissipated by the auxiliary amplifier, and due to improved gain accuracy, the power added efficiency (PAE) can be increased.…”

“…In order to obtain a closed loop gain of -5 (13.98dB), the input resistance R S has been chosen as 400Ω and the feedback resistance R F as 2kΩ. According to the theory presented in [11,12] the required negative impedance for linearization can be calculated as…”

“…Among these new techniques, due to its significant advantages for fully monolithic design, the active auxiliary compensation has received a great deal of attention. The negative impedance linearization technique presented in [11,12] uses a twochannel active compensation scheme, where the main amplifier provides the forward gain while the auxiliary amplifier functions as a negative impedance performing nonlinearity compensation. As discussed in [11,12], the technique has many advantages over the existing linearization methods.…”

“…The negative impedance linearization technique presented in [11,12] uses a twochannel active compensation scheme, where the main amplifier provides the forward gain while the auxiliary amplifier functions as a negative impedance performing nonlinearity compensation. As discussed in [11,12], the technique has many advantages over the existing linearization methods. However, the additional amplifier to implement the negative impedance causes more power dissipation; hence the power efficiency of the amplifier may be degraded.…”