using dense and regular fabrics such as crossbar is promising in terms of integration density, performance and power dissipation. Among the emerging alternatives to CMOS, molecular electronics based "diode-resistor logic" has generated considerable interest in recent times. However, some major challenges associated with circuit design using molecular switches are: 1) high defect rate; 2) lack of voltage gain of these switches that prevent logic cascading; and 3) large output voltage level degradation that affect robustness of operation. In this paper, we analyze the issue of input-dependent logic level degradation in diode-resistor style molecular crossbar and develop a simple analytical model for fast and accurate estimation of logic level degradation in a circuit. We also propose a voltage level-aware circuit design technique that limits the worst-case output level degradation. We verify the model by SPICE simulation which shows an average absolute error of less than 2%. Moreover, the proposed design technique improves the logic degradation level from 27% to 7% on an average compared to conventional design. Keywords: Diode-resistor logic, logic-level degradation, nano-crossbar circuit, robust circuit design.