An analog circuit on a flexible substrate is demonstrated for integration with charge sensitive chemical and biochemical sensors. A preamplifier circuit based on low temperature poly-Si thin film transistors (LTPS TFT) for integration with an extended gate ion sensitive field effect transistor (EG-ISFET) has been realized on a flexible polyimide substrate. This circuit, where sensors and preamplifiers are integrated on the same die, is intended for bio-sensing and wearable applications where the flexibility has an advantage.