Design Note 28 Issue 2 January 1996 6W Inverter for MOS Logic supplies The inverter is a simple push-pull circuit which takes advantage of the high curre nt handling capability of the ZTX650 range. It oscillates at a frequency of approximately 25kHz to allow it to use a very small transformer (RM6), and also to render the inverter inaudible. The output characteristics are given in Figures 2 and 3. Output ripple is approximately 150mV peak to peak on both outputs. The 6W inverter shown in Figure 1 has been designed to generate the extra power supplies required by popular MOS memories from a normal 5V TTL supply source. It may be used to supply up to eight 2808 read only memories which require supplies of +5V, -5V and +12V, or if the output components of the 12V section are reversed, the circuit will power over ten 5204 ROMs which require +5V and -12V supplies. ZTX650 7T 0.15mF 2T +12V * BY206 5T BY206 68mF 16V * 1K 6T 200 0V 33 + 6T 2T 5T BY206 7T BY206 * ZTX650 TFR1 100mF 10V 0V 100mF 10V 680 -5V Transformer details: FX3437 cores wound with: 2-0-2t, 29swg. 5-0-5t, 26swg. Bifilar 13-6-0-6-13t, 29swg. * REVERSE POLARITY IF -12V SUPPLY IS REQUIRED +5V Figure 1 6W Inverter Schematic. DN28- 1 Design Note 28 Issue 2 January 1996 Figure 2 Output characteristics of +12V Supply against Load Current. Figure 3 Output characteristics of -5V Supply against Load Current. Table 1. Output Voltage of +12V Supply against Load Current. Output Current Output voltage Output voltage 10 12.2 12.1 100 11.8 11.6 200 11.6 11.4 300 11.4 11.2 400 11.2 11.0 500 10.8 10.7 600 10.6 - 10mA load on -5V supply. 250mA load on -5V supply. DN28 - 2