This paper exploits tunnel field-effect transistors (TFET) unique asymmetrical device characteristics, demonstrating discriminant circuits for pattern recognition useful in machine learning-based VLSI and IoT designs. In contrast to unidirectional current conduction in TFET, it exhibits significant p-i-n leakage current with increase in negative drain-to-source voltage. Due to this characteristics, TFET transmission gate exhibits distinct behavior. Exploiting this behavior, a ring oscillator is designed that can sense the changes in operating frequency with response to the pattern of control bits. Utilizing this ring oscillator, a discriminant circuit is demonstrated which is highly energy efficient with an ultra-low energy consumption of 34.5 pJ at supply voltage of 0.4 V and much suits the demands of emerging machine learning-based VLSI systems. The simplicity of discriminant circuit makes the architecture of pattern recognition engine simpler and reduces the energy overheads.