Eitake Ibaragi

A CMOS Analog Multiplier Free from Mobility Reduction and Body Effect

This paper proposes a novel CMOS analog multiplier. As its significant merit, it is free from mobility reduction and body effect. Thus, the proposed multiplier is expected to have good linearity, comparing with conventional multipliers. Four transistors operating in the linear region constitute the input cell of the multiplier. Their sources and backgates are connected to the ground to cancel the body effect. Their gates are fixed to the same bias voltage to remove the effect of the mobility reduction. Input signals are applied to the drains of the input cell transistors through modified nullors. The simulation results show that THD is less than 0.8% for 0.6 Vp-p input signal at 2.5 V supply voltage, and that the 3 dB bandwidth is up to about 13.3 MHz.

A 1-MHz 7th-order continuous-time lowpass filter using very low distortion CMOS OTAs

In this paper, a 1-MHz 7th-order Butterworth lowpass filter is designed. The filter is composed of very low distortion CMOS OTAs. The linearity of the OTA is free from mobility reduction and body effect. This is the reason that the OTA shows low distortion characteristics. Thus, the lowpass filter also has low distortion. We confirmed that the filter exhibited very low distortion by simulation. When an input signal with 1 V (peak-peak) and 333 kHz is applied, THD of the lowpass filter becomes only 0.094%.

A novel CMOS OTA free from mobility reduction effect

Distortion of OTAs is caused by nonideal factors such as the mobility reduction effect, channel length medulation, transistor mismatch and so on. The transfer function of the proposed OTA is free from the mobility reduction effect. Thus, the proposed OTA is expected to have better linearity than conventional OTAs.

A Low Power Dissipation Technique for a Low Voltage OTA

This paper proposes a novel low power dissipation technique for a low voltage OTA. A conventional low power OTA with a class AB input stage is not suitable for a low voltage operation (±1.5 V supply voltages), because it uses composite transistors (referred to CMOS pair) which has a large threshold voltage. On the other hand, the tail-current type OTA needs a large tail-current value to obtain a sufficient input range at the expense of power dissipation. Therefore, the conventional tail-current type OTA has a trade-off between the input range and the power dissipation to the tail-current value. The trade-off can be eliminated by the proposed technique. The technique exploits negative feedback control including a current amplifier and a minimum current selecting circuit. The proposed technique was used on Wangs OTA to create another OTA, named Low Power Wangs OTA. Also, SPICE simulations are used to verify the efficiency of Low Power Wangs OTA. Although the static power of Low Power Wangs OTA is 122 μW, it has a sufficient input range, whereas conventional Wangs OTA needs 703 μW to obtain a sufficient input range. However, we can say that as the input signal gets larger, the power of Low Power Wangs OTA becomes larger.

A CMOS OTA free from second order effects with a high input resistance Gm control terminal

This paper proposes a CMOS OTA free from second order effects such as mobility reduction and body effects. The conventional OTA free from second order effects has a problem that the input resistance of transconductance control terminal is considerably low. When OTA-C filters are designed, many OTA transconductances are controlled by one voltage in order to tune their characteristics such as cut-off frequency and quality factor. Thus, the voltage source to control transconductance must have high current drive ability. The proposed OTA is based on the conventional approach, and it has a high input resistance transconductance control terminal.