6SL7 twin triode, phas splitter, differential amplifier, longtail
กำหนดให้ VRtail = 25% ของ B2+ , กำหนดให้ B2+ = 240V
VRtail = 25*240/100 = 60V
VHT = 240-60 = 180V
Imax. 1.5mA,
RL = 180V/1.5mA = 120K
กึ่งกลางวงสวิง 159+36/2 = 97.5V เลือก 100V
Vp 100V , Ia 0.67mA , Vg -1.2V
ใช้ Rk ร่วมกัน
Ik = 0.67*2 = 1.34mA
Rk = 1.2V/1.34mA = 895R/0.002W = 910R/ 1/4W
VRtail = 60V
VRk = 60+1.2 = 61.2V
Vp ground = 61.2+100 = 161.2V
VRL = 0.67mA*120K = 80.4V
B2+ = 161.2+80.4 = 241.6V
Rp = 115-85V/0.9-0.45mA = 30/0.45 = 67V/mA = 67K
RL/Rp = 120K/67K = 1.8
Gm = 0.87-0.35mA/1.5-1V = 0.52/0.5 = 1.04mA/V
u = Gm*Rp = 1.04*67 = 70
Rp eff. = Rp+Rk(u+1) = 67K+0.91K(70+1) = 67K+65K = 132K
gain = u*RL/Rp eff.+RL = 70*120K/132K+120K = 8400K/252K = 33
การทนกำลังของ RL = 80.4V*0.67mA = 0.05W ใช้ 120K/ 1/4W
