Abstract: A programmable generator is proposed that can achieve the unipolar and the ambipolar sigmoid functions with its derivatives.The proposed generator is a simple structure,composed of a translinear loop circuit and two differential transconductance circuits.The circuit can realize the unipolar and the ambipolar sigmoid functions output,adjust the amplitude,the gain factor and the threshold of the generated function through changing external bias current or voltage,and the current or voltage can be selected as output signal,thus,the generator has been widely used in various current-mode or voltage-mode neural networks.PSPICE simulation test is employed with TSMC 0.35μm CMOS standard technology to verify the circuit validity.The results show a good fitting degree between the generated functions with its derivatives and ideal functions,and have the advantages of wide application range and good programmability for the proposed circuit.