The MAX4805/MAX4805A are octal high-voltage-protected operational amplifiers. These devices are a fully integrated, very compact solution for in-probe amplification of echo signals coming from transducers in an ultrasound system. The use of in-probe buffering improves system signal-to-noise ratio (SNR) for transducers featuring high-output impedance. This results in greater penetration depth and sensitivity. The MAX4805/MAX4805A can be adopted in ultrasound probes without any change in the system (scanner machine). Typical applications include high-impedance piezoelectric transducers (PZT) and capacitive micromachined ultrasonic transducers (CMUT) in-probe buffering and amplification. The MAX4805 is optimized for PZT applications, and the MAX4805A is optimized for CMUT applications.
The MAX4805/MAX4805A feature eight operational amplifiers configured in a noninverting configuration. The small-signal output impedance of these operational amplifiers is 65Ω (typ) for matching the typical cable impedance. The low-noise amplifier features 44MHz (typ) -3dB bandwidth and very low voltage and current noise, ensuring excellent noise figure. The output signals of these operational amplifiers are limited with diodes in an antiparallel configuration to GND.
The MAX4805/MAX4805A provide HV protection for inputs and outputs of the operational amplifiers. The operational amplifiers inputs are protected by an external HV capacitor. An integrated automatic high-voltage switch protects the output of the amplifier from HV bursts. Transmitted bursts reach the transducer through a pair of integrated, antiparallel diodes. Each channel is able to sustain transmission burst up to ≤ 100V. The high-voltage (HV) protection is automatically activated as soon as the TX voltage is greater than ±2.7V (typ); no dedicated TX/RX signal is required.
The MAX4805 and the MAX4805A differ in terms of input-current noise, input impedance, and voltage gain. Depending on the equivalent transducer source impedance, either the MAX4805 or the MAX4805A can be used to optimize a better noise figure.
The MAX4805/MAX4805A are available in the 32-pin TQFN package. All devices are specified for the commercial 0°C to +70°C temperature range.
Applications
- Ultrasound Imaging, PZT NDT Probes
- Ultrasound Medical Imaging, CMUT Probes
- Ultrasound Medical Imaging, PZT HF Probes
(typ) (MAX4805)