A Full-Oxide CMOS Operational Amplifier Based on n-Type IGZO and p-Type SnO Thin-Film Transistors

Oxide semiconductors have a promising potential in future wearable, transparent, and flexible electronics, but the research to date is mostly limited to n-type thin-film transistors (TFTs) and circuits. Here, an entirely oxide-semiconductor-based complementary operational amplifier (op-amp) is developed, comprising n-type indium-gallium-zinc-oxide (IGZO) and p-type tin monoxide (SnO). The IGZO TFTs show a mobility of 21.5 cm2/
$\text{V}\cdot \text{s}$
, a threshold voltage of 4.8 V, and a subthreshold swing of 0.2 V/decade. The SnO TFTs exhibit a mobility of 1.19 cm2/
$\text{V}\cdot \text{s}$
and a threshold voltage of −3.5 V. The op-amp takes an area of
$500\times 250\,\,\mu \text{m}$
. Operating under a ±12-V supply, the op-amp achieves a negative-feedback gain of 54 dB, the highest among the reported op-amps based on oxide semiconductor TFTs. The power consumption of the op-amp is 0.2 mW. The op-amp also exhibits a unit-gain frequency of 300 kHz, a bandwidth of 9 kHz, and a gain-bandwidth product (GBWP) of 4.5 MHz.