{"type_number":"EF94","canonical_url":"https://tubeofile.com/tubes/EF94","manufacturer":"Mullard","tube_type_key":"ss_pentode","tube_type_display_name":"Small Signal Pentode","base_name":"B7G","description":"Sharp-cutoff RF/IF pentode for use as a high-gain radio-frequency or intermediate-frequency amplifier. Low grid-plate capacitance and high transconductance make it suited for high-frequency wide-band applications up to 50 MHz. Also used as audio voltage amplifier.","is_directly_heated":false,"completeness":"high","notes":["Suppressor grid (g3) is internally connected to cathode.","HF94 (12.6 V heater) and XF94/3AU6 (different heater ratings) are related types but not pin-for-pin equivalents due to different heater voltages.","Triode-strapped data sourced from Tom Schlangen's 'Pentodes Strapped as Triodes' (2009) measurements, not from the manufacturer datasheet.","Vhk_max is 100 V DC (cathode positive relative to heater); some 6AU6A variants are rated to 200 V."],"references":["https://frank.pocnet.net/sheets/020/6/6AU6.pdf","https://frank.pocnet.net/sheets/093/6/6AU6A.pdf"],"source_urls":{"r_type":"http://www.r-type.org/exhib/aaa0264.htm","tdsl":"http://tdsl.duncanamps.com/show.php?des=EF94","radiomuseum":"https://www.radiomuseum.org/tubes/tube_ef94.html"},"raw_equivalents":["6AU6","6AU6A","6136","6J4P","CV2524"],"equivalents":[],"similar":[{"type_number":"3AU6","reason":"Related type with different heater ratings — not pin-for-pin equivalent","has_detail_page":false},{"type_number":"HF94","reason":"Related type with 12.6V heater — not pin-for-pin equivalent due to different heater voltage","has_detail_page":true},{"type_number":"XF94","reason":"Related type with different heater ratings — not pin-for-pin equivalent","has_detail_page":true}],"pins":[{"pin_number":"1","function":"Control Grid","function_code":"g1","notes":null},{"pin_number":"2","function":"Suppressor Grid (g3, internally connected to cathode)","function_code":"g3","notes":null},{"pin_number":"3","function":"Heater","function_code":"h","notes":null},{"pin_number":"4","function":"Heater","function_code":"h","notes":null},{"pin_number":"5","function":"Anode","function_code":"a","notes":null},{"pin_number":"6","function":"Screen Grid","function_code":"g2","notes":null},{"pin_number":"7","function":"Cathode","function_code":"k","notes":null}],"specs":[{"key":"Vh","display_name":"Heater Voltage","value":"6.3","numeric_value":"6.3","unit":"V","param_group":"heater"},{"key":"Ah","display_name":"Heater Current","value":"0.3","numeric_value":"0.3","unit":"A","param_group":"heater"}],"sections":[{"section_number":1,"section_label":"Pentode","tube_type_key":"ss_pentode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Vs_max","display_name":"Screen Voltage (max)","value":"300","numeric_value":"300","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"3.2","numeric_value":"3.2","unit":"W","param_group":"absolute_max"},{"key":"Ps_max","display_name":"Screen Dissipation (max)","value":"0.65","numeric_value":"0.65","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"20","numeric_value":"20","unit":"mA","param_group":"absolute_max"},{"key":"Vhk_max","display_name":"Heater-to-Cathode Voltage (max)","value":"100","numeric_value":"100","unit":"V","param_group":"absolute_max"},{"key":"Rg_max","display_name":"Max Grid Resistor","value":"1","numeric_value":"1","unit":"MΩ","param_group":"absolute_max"},{"key":"Va","display_name":"Anode Voltage (typical)","value":"250","numeric_value":"250","unit":"V","param_group":"typical_operating"},{"key":"Vs","display_name":"Screen Voltage (typical)","value":"150","numeric_value":"150","unit":"V","param_group":"typical_operating"},{"key":"Vg","display_name":"Grid 1 Bias Voltage","value":"-1","numeric_value":"-1","unit":"V","param_group":"typical_operating"},{"key":"mAa","display_name":"Anode Current","value":"10.8","numeric_value":"10.8","unit":"mA","param_group":"typical_operating"},{"key":"mAs","display_name":"Screen Current","value":"3.0","numeric_value":"3","unit":"mA","param_group":"typical_operating"},{"key":"ra","display_name":"Anode Resistance","value":"1000000","numeric_value":"1000000","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"5.2","numeric_value":"5.2","unit":"mA/V","param_group":"typical_operating"},{"key":"Cgp","display_name":"Grid-to-Plate Capacitance","value":"0.0035","numeric_value":"0.0035","unit":"pF","param_group":"capacitances"},{"key":"Cin","display_name":"Input Capacitance","value":"5.5","numeric_value":"5.5","unit":"pF","param_group":"capacitances"},{"key":"Cout","display_name":"Output Capacitance","value":"5.0","numeric_value":"5","unit":"pF","param_group":"capacitances"}]},{"section_number":2,"section_label":"Triode Strapped","tube_type_key":"small_signal_triode","specs":[{"key":"Va_max","display_name":"Anode Voltage (max)","value":"150","numeric_value":"150","unit":"V","param_group":"absolute_max"},{"key":"Pa_max","display_name":"Anode Dissipation (max)","value":"3.0","numeric_value":"3","unit":"W","param_group":"absolute_max"},{"key":"Ik_max","display_name":"Cathode Current (max)","value":"20","numeric_value":"20","unit":"mA","param_group":"absolute_max"},{"key":"ra","display_name":"Anode Resistance","value":"7500","numeric_value":"7500","unit":"Ω","param_group":"typical_operating"},{"key":"gm","display_name":"Transconductance","value":"4.8","numeric_value":"4.8","unit":"mA/V","param_group":"typical_operating"},{"key":"mu","display_name":"Amplification Factor (μ)","value":"36","numeric_value":"36","unit":"—","param_group":"typical_operating"}]}],"synced_at":"2026-04-07T12:42:24.919Z"}