| LM231 | National Semiconductor | Precision Voltage-to-Frequency Converter |
| LM231AN | National Semiconductor | Precision Voltage-to-Frequency Converter |
| LM231N | National Semiconductor | Precision Voltage-to-Frequency Converter |
| LM331 | National Semiconductor | Precision Voltage-to-Frequency Converter |
| LM331AN | National Semiconductor | Precision Voltage-to-Frequency Converter |
| LM331N | National Semiconductor | Precision Voltage-to-Frequency Converter |
| LM331 MDC | National Semiconductor | |