Aiming at the problem that it is difficult to detect the weak electrical signal generated in the process of acoustic electrical conversion of capacitive micromachined ultrasonic transducer（CMUT）

two kinds of weak signal detection circuits are proposed

one is charge amplification circuit based on charge detection principle

and the other is trans resistance amplification circuit based on current detection principle.First

the transient and AC small signal characteristics of the two circuits are simulated and tested

and then the two circuits are connected with CMUT transducer respectively for ultrasonic signal detection test.The test results show that the

circuit has high gain characteristics

and the amplification factor is 1×10

11

.The signal-to-noise ratio is 20.57 dB.The transimpedance amplifier converts and amplifies the weak current signal from CMUT transducer into voltage signal through feedback resistance.The amplification factor is 560 and the signal-to-noise ratio is 38.05 dB.The transimpedance amplifier uses the feedback capacitor to introduce poles

which increases the stability of the circuit.Through the comparison of theory

simulation and actual test

the trans impedance amplifier circuit is more suitable for the detection and amplification of CMUT transducer weak signal.