宽范围线性可调OTA的设计及应用

为了解决基本差分式OTA输入范围有限，跨导不能线性调节且调节范围不宽的问题，采用两个平方电路分别为两个基本差分式OTA提供偏置电流，实现了一种跨导宽范围线性可调全差分OTA（LOTA）。通过引入参考电流，解决了电压输入范围和跨导调节范围不能同时增大的矛盾，同时又实现了跨导增益从负到正的范围内连续线性调节。作为应用，利用提出的LOTA作为基本模块实现的二阶通用滤波器可实现极点频率连续线性调节。电路的性能通过PSPICE仿真得到了验证。

Design and application of widely and linearly tunable OTA

In order to solve the problems of the basic differential OTA, which has the limited input ranges, narrow tunable ranges and inability to linearly tune the transconductance gain, a new CMOS Operational Transconductance Amplifier（OTA） called LOTA is proposed, of which the transconductance gain can be widely and linearly tuned. The design method is achieved by employing two square circuits for bias of two basic differential CMOS OTAs respectively. By setting a reasonable reference current, not only the input voltage swing and the adjusting range of the gain can get a wide value at the same time, but also the transconductance gain can be continuously and linearly adjusted from a negative value to a positive one through the external bias currents. The proposed LOTA is employed to implement a second-order universal current-mode filter as an application. The performance of the LOTA and the filter is verified through PSPICE simulation results.