Design of Op Amp Operating in Sub Threshold Region using 90nm Technology
Op-Amps are being widely used in most of the electronic devices today varying from medical, industrial, scientific and consumer purposes. The world is now using the technology that develops more and more portable devices. The world follows the Moore's law and due to the scaling down of the transistor channel length more number of transistors can be integrated. This necessitates more battery life of the device by reducing the power consumption of each transistor. As op amps form the integral part of the circuit , by using a low power op amp can help in this power consumption of the whole device.
The power dissipation can be made minimal either by reducing the circuit supply voltage or by bringing down the total current in the circuit or by bringing down both. Also scaling down of the devices to nanotechnology makes the low supply voltage necessary. But reducing the voltage to a very low value is not possible as the threshold voltage of the circuit will not get reduced in the same rate as that of supply voltage. So by reducing the current to the level of sub threshold current an ultra low-power op amp can be designed whose power consumption will be in the order of nano Watts.
The current in the sub threshold region of the transistors will be in the order of nano Ampere. The op amps working in sub threshold region is hence gaining attention which helps the circuit to operate under low voltage and low power. The low power op amp designed in the sub threshold region will create speed problem as the slew rate of the device will be very less due to minimum current flowing in the device. But for biomedical and sensor applications like electrocardiogram, electromyography, electroencephalography etc where the speed is not a limiting factor but the power dissipation is, there the low power op amps will be of great use.
Keywords - Sub Threshold Region, Low Power Op Amp, Cadence, Diffusion Current