Noise Margins of I2L, SI2L, ISL and STL

I²L, SI²L, ISL and STL are bipolar logic types which operate with a relatively small 2 voltage swing. I²L has a voltage swing of about 500-700 mv, while the other types have 140-400 mV. Fig.1 shows the gate symbol and the principle schematics; the saturation currents of the transistors and diodes are indicated with I_no ,I_po , I_do, , etc. The internal current sources in I²L and SI²L are saturated pnp transistors with the base grounded, while the internal current sources in ISL and STL are non-saturated pnp transistors (base at a ref. voltage) or resistors. The noise margins of these logics are often subject of confusion. This paper intends to clear up this confusion by the introduction of principle noise schemes and by presenting some noise margin data.