and, as it will be used a lot, define the determinant Δ=S11S22−S12S21Δ=S11S22−S12S21\Delta = S_{11}S_{22} − S_{12}S_{21}. The overall amplifier has scattering parameters S'S′\mathbf{S}′. ΓSΓS\Gamma_{S} is the generator reflection coefficient and ΓLΓL\Gamma_{L} is the reflection coefficient of the load. For unconditional stability, |S′11|<1|S11′|<1|S'_{11}| < 1 and |S′22|<1|S22′|<1|S'_{22}| < 1. If |S′11|>1|S11′|>1|S'_{11}| > 1 or |S′22|>1|S22′|>1|S'_{22}| > 1, then there is a negative resistance and oscillation could possibly occur. Unconditional stability is defined as when |S′11|<1|S11′|<1|S'_{11}| < 1 for all passive loads ΓLΓL\Gamma_{L} (i.e., |ΓL|≤1)|ΓL|≤1)|\Gamma_{L}|\leq 1 ) and |S′22|<1|S22′|<1|S'_{22}| < 1 for all passive source impedances ΓSΓS\Gamma_{S} (i.e., |ΓS|≤1)|ΓS|≤1)|\Gamma_{S}|\leq 1 ). These inequalities are the same as saying the real part of the input and output impedances of the amplifier are positive resistances.