hi all
I have recently completed a project which uses a TDA2003 amplifier. It works quite well. However It tends to go into oscillation if i go much over 50% on the volume control. I have the data sheet for the TDA and if i have followed it correctly then R15 in my circuit should be 20*R17 which is 94R. 100R is the nearest value and i have changed R17 from the 120R to 100R. It has allowed me to open the volume more but i get oscillation further up the scale. The oscillation is also, now, at a higher frequency it seems. The capacitor C18 should have been an 8n2 but these proved difficult to get hold of so i was advised a 10nF would suffice. Its my understanding that the capacitor effects the frequency range of the output. correct me if im wrong please. I understand the equation for Cx as seen on the data sheet but do not know what 'B' stands for in the lower line. anyway 82R is the next nearest down resistor i could try. Am i doing this correctly? The amplifier layout and components as seen in the attached picture is based on the velleman kit MK4001 7W amplifier. The PCB layout of the amp follows the original PCB that came with the kit. help and guidance would be appreciated, thank you.
I have marked the resistors in question with the notations from the data sheet for clarification. the only thing i have notice is that C18 and R15 although strung between pin 2 and 4 of the TDA in the velleman schematic and the official datasheet for the TDA their positions are reversed is this critical?
the signal to the amp is from a LM358 which passes through a 4066/7555 circuit which adds a chopping effect to the input from an electret mic.
Regards
Fenris
I have recently completed a project which uses a TDA2003 amplifier. It works quite well. However It tends to go into oscillation if i go much over 50% on the volume control. I have the data sheet for the TDA and if i have followed it correctly then R15 in my circuit should be 20*R17 which is 94R. 100R is the nearest value and i have changed R17 from the 120R to 100R. It has allowed me to open the volume more but i get oscillation further up the scale. The oscillation is also, now, at a higher frequency it seems. The capacitor C18 should have been an 8n2 but these proved difficult to get hold of so i was advised a 10nF would suffice. Its my understanding that the capacitor effects the frequency range of the output. correct me if im wrong please. I understand the equation for Cx as seen on the data sheet but do not know what 'B' stands for in the lower line. anyway 82R is the next nearest down resistor i could try. Am i doing this correctly? The amplifier layout and components as seen in the attached picture is based on the velleman kit MK4001 7W amplifier. The PCB layout of the amp follows the original PCB that came with the kit. help and guidance would be appreciated, thank you.
I have marked the resistors in question with the notations from the data sheet for clarification. the only thing i have notice is that C18 and R15 although strung between pin 2 and 4 of the TDA in the velleman schematic and the official datasheet for the TDA their positions are reversed is this critical?
the signal to the amp is from a LM358 which passes through a 4066/7555 circuit which adds a chopping effect to the input from an electret mic.
Regards
Fenris
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