A Micropowered IC modulator for biomedical telemetry

A MICROPOWERED, monolithic, pulse-frequency modulator circuit which is compensated against variations in operating frequency with changes in supply voltage has been developed. The circuit was designed for application in implantable temperature or biopotential (EMG and ECG) telemetry systems where micropower operation is essential. The circuit diagram is given in Figure 1 and a photomicrograph of the chip is shown in Figure 2. The circuit consists of two major subsections. The left-hand side is a modified, comp1ementar.y. astable multivibrator circuit and the right-hand side is a differential amplifier-current difference.