6SL7 pre-drive
V cut off = 230V, I sat. = 3.5mA
RL = 230V/3.5mA = 65.7K = 68K
วงสวิง 224-89V = 135V
กริดสวิง 3.5V
Av = 135/3.5 = 38.6
กึ่งกลางวงสวิง 224+89/2 = 156.5V เลือก 155V
Vp = 155V , Ia = 1.15mA , Vg = -1.5V
Rk = 1.5V/1.15mA = 1.3K = 1.2K
Rp = 165-140V/1.32-0.55mA = 25/0.77 = 32.5V/mA = 32.5K
RL/Rp = 68K/32.5K = 2.1
Gm = 1.92-0.55mA/2-1V = 1.37/1 = 1.37mA/V
u = Gm*Rp = 1.37*32.5 = 44.5
Rp eff. = Rp+Rk(u+1) = 32.5K+1.2K(22.5+1) = 32.5K+28.2K =60.7K
gain = u*RL/Rp eff.+RL = 44.5*68K/60.7K+68K = 3026K/128.7K = 23.5
B2+ = 1.5V+155V+(1.15mA*68K) = 156.5+78.2 = 234.7V
Vp gnd. = 156.5V