A Unity-Gain Buffer with 1.6GHz Bandwidth and $1900\mathrm{V}/\mu \mathrm{s}$ Slew Rate based on an OPA Adopting Cascaded Class-AB Structure

A wideband and high slew rate (SR) unity-gain buffer (UGB) with the capability to drive a heavy load is proposed in this brief. An operational amplifier (OPA) is configured as unity gain negative feedback to improve the bandwidth and gain accuracy. A complementary input stage and cascaded class-AB output stage are adopted to enhance the small-signal bandwidth and SR of the OPA. The UGB is implemented in the $0.18-\mu\mathrm{m}$ SiGe BiCMOS technology and achieves a −3 dB bandwidth of 1.6 GHz, and an average SR of $1900\ \mathrm{V}/\mu\mathrm{s}$ with 5 V supply voltage and $100\ \Omega$ load resistance. The quiescent current of the core amplifier is 3.8 mA.