A 1.2 V NPN-only log-domain integrator

A simple log-domain integrator that operates nominally with a supply voltage of 1.2 V is proposed. It does not employ PNP or PMOS transistors in the signal path. This has two advantages: i) It makes the integrator suitable for high-frequency applications. ii) The circuit can be implemented using cheap bipolar processes rather than the more expensive BiCMOS processes or the bipolar processes featuring high-quality PNP transistors. A third-order Chebyshev prototype filter, employing the proposed integrator, is realized using a semi-custom bipolar array. It consumes 282 /spl mu/A per pole for a cutoff frequency of 1.5 MHz. For lower biasing currents, the circuit can operate from a supply voltage as low as 0.9 V. Detailed experimental results are reported.