A Fully-Printed Self-Biased Polymeric Audio Amplifier for Driving Fully-Printed Piezoelectric Loudspeakers

In this paper, a printed audio amplifier, which is a new application for organic electronics, is suggested. The amplifier consists of several fully-printed bendable components including: a loudspeaker, organic field effect transistors (OFETs), capacitors, and resistors. All components are fabricated on polyethylene terephthalate (PET) substrate by means of high-throughput printing techniques. A complete self-biased circuit is reported consisting of large multi-finger OFETs with channel length of 20
$\mu\text{m}$
and total width of 0.475 meter. The amplifier provides a peak voltage gain of 18 dB at 400 Hz, can reproduce sound pressure level of 36–60 dBA over 700 Hz to 12.5 kHz at one meter distance, and has a unity-gain-bandwidth of 17.7 kHz/5.2 kHz when driving 0 nF/
$\sim$
39 nF load at
$\text{V}_{\mathrm{DD}}=80\ \text{V}$
, respectively. The impact of bias-stress effects on the amplifier performance is measured to be
$\sim$
3 dBA sound loss after 5 hours of continuous operation. The whole circuit is packaged and laminated on a separate PET sheet. In addition, the intrinsic electrical impedance of the printed PVDF-TrFE piezoelectric polymer used in the loudspeaker is characterized, and is modeled by a complex dielectric constant.