1V powered small signal AC amplifier circuit

The attached figure is a circuit diagram of a small signal AC amplifier with a power supply voltage of only 1V and a gain of 5. NIV7015 is a CMOS operational amplifier produced by New Japan Radio, and the power supply voltage can be as low as 1V under single power supply working conditions.

This op amp is a full-swing op amp. Although there are no relevant parameters when the power supply voltage is IV in the data sheet, when using it, you can refer to the values ​​of the common-mode input voltage VICM=0V~0.5V, the maximum output voltage amplitude VOM1=VDD-0.lV, VOM2=Vss+0.lV to design the circuit.

For general full-rail output op amps, the bias voltage is set to VCC/2 or VDD/2. However, in this circuit, if VDD/2 is set, the dynamic range of the positive and negative half-cycles of the output signal will be seriously asymmetric, and the positive half-cycle will be limited very early.

To do this, the DC bias voltage at the input must be adjusted.

In this circuit, resistors R2 and R8 are used to divide the input DC bias voltage to set it to one-fourth of the power supply voltage VDD. The DC bias voltage is sent to the non-inverting input terminal of the non-inverting amplifier circuit after passing through R6. The DC gain of the op amp is set to twice based on the ground, so the DC output voltage at the output terminal is half of the power supply voltage VDD. However, if the AC gain of the circuit is also set to twice, its AC gain will be too small. Therefore, the resistors that set the amplifier gain are divided into two parts, R1 and R3, in the circuit, and a 1μF AC bypass electrolytic capacitor is connected in parallel at both ends of the resistor R3 to set the DC gain and AC gain of the amplifier to different values.

The AC gain of the circuit shown is 5 times. The input impedance is 470kΩ, the output voltage is about 1Vpp, the power supply voltage is 1V, and the current consumption is 10mA.