{"id":1558,"date":"2018-07-06T04:49:13","date_gmt":"2018-07-06T04:49:13","guid":{"rendered":"https:\/\/hocvienit.vn\/?p=1558"},"modified":"2025-01-04T16:42:19","modified_gmt":"2025-01-04T09:42:19","slug":"phan-tich-mach-khuyech-dai-am-thanh-co-ban-dung-bjt","status":"publish","type":"post","link":"https:\/\/hocvienit.vn\/?p=1558","title":{"rendered":"Ph\u00e2n t\u00edch m\u1ea1ch khu\u1ebfch \u0111\u1ea1i \u00e2m thanh c\u01a1 b\u1ea3n d\u00f9ng BJT"},"content":{"rendered":"
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T\u00ean m\u1ea1ch<\/strong>: Khu\u1ebfch \u0111\u1ea1i \u00e2m t\u1ea7n s\u1eed d\u1ee5ng Transistor l\u01b0\u1ee1ng h\u1ea1t (BJT).<\/span><\/span><\/p>\n

\"Khu\u1ebfch
Khu\u1ebfch \u0111\u1ea1i \u00e2m t\u1ea7n s\u1eed d\u1ee5ng Transistor l\u01b0\u1ee1ng h\u1ea1t (BJT)<\/figcaption><\/figure>\n

T\u00e1c d\u1ee5ng linh ki\u1ec7n<\/strong><\/span><\/h2>\n
    \n
  • C1:<\/strong> D\u1eabn t\u00edn hi\u1ec7u v\u00e0o.\u00a0<\/span><\/li>\n
  • C6:<\/strong> T\u1ee5 l\u1ecdc ngu\u1ed3n ch\u00ednh, gi\u00e1 tr\u1ecb c\u1ee7a C6 ph\u1ee5 thu\u1ed9c v\u00e0o d\u00f2ng t\u1ea3i, n\u00f3i c\u00e1ch kh\u00e1c ph\u1ee5 thu\u1ed9c v\u00e0o c\u00f4ng su\u1ea5t ho\u1ea1t \u0111\u1ed9ng c\u1ee7a m\u1ea1ch. M\u1ea1ch c\u00f3 c\u00f4ng su\u1ea5t c\u00e0ng l\u1edbn, \u0103n d\u00f2ng c\u00e0ng l\u1edbn th\u00ec C6 ph\u1ea3i c\u00f3 gi\u00e1 tr\u1ecb c\u00e0ng cao. N\u1ebfu kh\u00f4ng, s\u1ebd g\u00e2y hi\u1ec7n t\u01b0\u1ee3ng “\u0111\u1eadp m\u1ea1ch” c\u00f3 ngh\u0129a l\u00e0 \u0111i\u1ec7n \u00e1p tr\u00ean C6 b\u1ecb nh\u1ea5p nh\u00f4 v\u00e0 loa s\u1ebd ph\u00e1t sinh ti\u1ebfng \u00f9_g\u1ecdi l\u00e0 \u00f9 xoay chi\u1ec1u. N\u1ebfu \u0111i\u1ec7n \u00e1p nu\u00f4i m\u1ea1ch \u0111\u01b0\u1ee3c c\u1ea5p b\u1edfi bi\u1ebfn \u00e1p 50Hz s\u1ebd nghe ti\u1ebfng \u00f9 (nh\u01b0 c\u00f2i t\u1ea7m), n\u1ebfu c\u1ea5p b\u1eb1ng bi\u1ebfn \u00e1p xung t\u1ea7n s\u1ed1 cao s\u1ebd nghe ti\u1ebfng r\u00edt.\u00a0<\/span><\/li>\n
  • R5-C3:<\/strong> H\u1ee3p th\u00e0nh m\u1ea1ch l\u1ecdc RC \u1ed5n \u0111\u1ecbnh ngu\u1ed3n c\u1ea5p v\u00e0 ch\u1ed1ng t\u1ef1 k\u00edch cho t\u1ea7ng k\/\u0111 2, 1. Tuy nhi\u00ean n\u1ebfu m\u1eafc \u1edf \u0111\u00e2y th\u00ec t\u00e1c d\u1ee5ng c\u1ee7a R5-C3 kh\u00f4ng cao. Mu\u1ed1n n\u00e2ng cao t\u00e1c d\u1ee5ng c\u1ee7a n\u00f3 b\u1ea1n ph\u1ea3i m\u1eafc m\u1eaft l\u1ecdc n\u00e0y v\u1ec1 ph\u00eda c\u1ef1c (+) c\u1ee7a C6.\u00a0<\/span><\/li>\n
  • R3-C2:<\/strong> M\u1ea1ch l\u1ecdc RC \u1ed5n \u0111\u1ecbnh ngu\u1ed3n, ch\u1ed1ng t\u1ef1 k\u00edch cho k\/\u0111 1 (k\/\u0111 c\u1eeda v\u00e0o).\u00a0<\/span><\/li>\n
  • R1-R2:<\/strong> \u0110\u1ecbnh thi\u00ean, ph\u00e2n \u00e1p \u0111\u1ec3 \u1ed5n \u0111\u1ecbnh ph\u00e2n c\u1ef1c t\u0129nh cho Q1, \u0111\u1ec3 Q1 ko g\u00e2y m\u00e9o tuy\u1ebfn t\u00ednh khi k\/d th\u00ec R1 ph\u1ea3i \u0111\u01b0\u1ee3c ch\u1ec9nh \u0111\u1ec3 Q1 l\u00e0m vi\u1ec7c \u1edf ch\u1ebf \u0111\u1ed9 A (t\u01b0\u01a1ng \u1ee9ng Ube Q1 ~ 0.8V \u0111\u1ed1i v\u1edbi BTJ g\u1ed1c silic). \u0110\u1ed3ng th\u1eddi R2 ph\u1ea3i \u0111\u01b0\u1ee3c ch\u1ecdn c\u00f3 gi\u00e1 tr\u1ecb b\u1eb1ng tr\u1edf kh\u00e1ng ra c\u1ee7a m\u1ea1ch \u0111\u1eb1ng tr\u01b0\u1edbc. N\u1ebfu t\u00edn hi\u1ec7u v\u00e0o l\u00e0 micro th\u00ec R2 c\u00f3 gi\u00e1 tr\u1ecb ch\u00ednh b\u1eb1ng tr\u1edf kh\u00e1ng c\u1ee7a micro.\u00a0<\/span><\/li>\n
  • R4:<\/strong> T\u1ea3i Q1, \u0111\u1ecbnh thi\u00ean cho Q2. Trong m\u1ea1ch n\u00e0y Q1 v\u00e0 Q2 \u0111\u01b0\u1ee3c gh\u00e9p tr\u1ef1c ti\u1ebfp \u0111\u1ec3 t\u0103ng h\u1ec7 s\u1ed1 k\/\u0111 d\u00f2ng \u0111i\u1ec7n tr\u01b0\u1edbc khi c\u00f4ng su\u1ea5t (Q2 \u0111\u00f3ng vai tr\u00f2 ti\u1ec1n k\/\u0111 c\u00f4ng su\u1ea5t). M\u1eb7t kh\u00e1c c\u0169ng \u0111\u1ec3 gi\u1ea3m m\u00e9o bi\u00ean \u0111\u1ed9 v\u00e0 m\u00e9o t\u1ea7n s\u1ed1 khi t\u1ea7n s\u1ed1, bi\u00ean \u0111\u1ed9 c\u1ee7a t\u00edn hi\u1ec7u v\u00e0o thay \u0111\u1ed5i.\u00a0<\/span><\/li>\n
  • R7-C4:<\/strong> H\u1ee3p th\u00e0nh m\u1ea1ch h\u1ed3i ti\u1ebfp \u00e2m d\u00f2ng \u0111i\u1ec7n c\u00f3 t\u00e1c d\u1ee5ng \u1ed5n \u0111\u1ecbnh h\u1ec7 s\u1ed1 k\/\u0111 d\u00f2ng \u0111i\u1ec7n cho Q1, gi\u1ea3m nh\u1ecf hi\u1ec7n t\u01b0\u1ee3ng m\u00e9o bi\u00ean \u0111\u1ed9. Khi \u0111\/ch\u1ec9nh gi\u00e1 tr\u1ecb c\u1ee7a C4 s\u1ebd thay \u0111\u1ed5i h\u1ec7 s\u1ed1 k\/\u0111 c\u1ee7a Q1, n\u00f3i c\u00e1ch kh\u00e1c \u0111\/c C4 s\u1ebd l\u00e0m m\u1ea1ch k\u00eau to_k\u00eau nh\u1ecf.<\/span><\/li>\n
  • Q1:<\/strong> K\/\u0111\u1ea1i t\u00edn hi\u1ec7u v\u00e0o, \u0111\u01b0\u1ee3c m\u1eafc theo ki\u1ec3u E chung.\u00a0<\/span><\/li>\n
  • Q2:<\/strong> \u0110\u00f3ng vai tr\u00f2 k\/\u0111 ti\u1ec1n c\u00f4ng su\u1ea5t \u0111\u01b0\u1ee3c m\u1eafc ki\u1ec3u C chung. T\u00edn hi\u1ec7u ra \u1edf ch\u00e2n E c\u1ea5p cho 2 BJT c\u00f4ng su\u1ea5t. \u1ede \u0111\u00e2y, th\u1ef1c ch\u1ea5t ko c\u00f3 t\u00edn hi\u1ec7u xoay chi\u1ec1u n\u00e0o h\u1ebft, ch\u1ec9 c\u00f3 \u0111i\u1ec7n \u00e1p m\u1ed9t chi\u1ec1u thay \u0111\u1ed5i (l\u00ean xu\u1ed1ng) quanh m\u1ee9c t\u0129nh ban \u0111\u1ea7u. T\u00edn hi\u1ec7u ra \u1edf ch\u00e2n E Q2 \u0111\u01b0\u1ee3c d\u00f9ng k\u00edch th\u00edch (th\u00f4ng qua thay \u0111\u1ed5i \u0111i\u1ec7n \u00e1p) cho Q3, Q4.\u00a0<\/span><\/li>\n
  • Q3, Q3:<\/strong> C\u1eb7p BJT c\u00f4ng su\u1ea5t \u0111\u01b0\u1ee3c m\u1eafc theo ki\u1ec3u “\u0111\u1ea9y k\u00e9o n\u1ed1i ti\u1ebfp”. Hai BJT n\u00e0y thay nhau \u0111\u00f3ng\/m\u1edf \u1edf t\u1eebng n\u1eeda chu k\u1ef3 c\u1ee7a t\u00edn hi\u1ec7u \u0111\u1eb7t v\u00e0o. L\u01b0u \u00fd l\u00e0 Q3 d\u00f9ng PNP, Q4 d\u00f9ng NPN nh\u01b0ng ph\u1ea3i c\u00f3 th\u00f4ng s\u1ed1 t\u01b0\u01a1ng \u0111\u01b0\u01a1ng nhau. Ki\u1ec3u m\u1eafc Q2, Q3, Q4 nh\u01b0 tr\u00ean g\u1ecdi l\u00e0 “\u0111\u1ea9y k\u00e9o n\u1ed1i ti\u1ebfp t\u1ef1 \u0111\u1ea1o pha”\u00a0<\/span><\/li>\n
  • R9, R10:<\/strong> \u0110i\u1ec7n tr\u1edf c\u1ea7u ch\u00ec, b\u1ea3o v\u1ec7 Q3, Q4 kh\u1ecfi b\u1ecb ch\u1ebft khi c\u00f3 1 trong 2 BJT b\u1ecb ch\u1eadp.\u00a0<\/span><\/li>\n
  • D1, D2:<\/strong> \u1ed4n \u0111\u1ecbnh nhi\u1ec7t, b\u1ea3o v\u1ec7 tr\u00e1nh cho Q3, Q4 b\u1ecb n\u00f3ng. C\u01a1 ch\u1ebf b\u1ea3o v\u1ec7 t\u00f4i ko gi\u1ea3i th\u00edch \u1edf \u0111\u00e2y, c\u00e1c b\u1ea1n t\u1ef1 xem l\u1ea1i l\u00fd thuy\u1ebft m\u1ea1ch BJT c\u01a1 b\u1ea3n. <\/span><\/li>\n
  • PR1:<\/strong> \u0110i\u1ec1u ch\u1ec9nh ph\u00e2n c\u1ef1c Q4, th\u00f4ng qua \u0111\u00f3 ch\u1ec9nh c\u00e2n b\u1eb1ng cho “\u0111i\u1ec7n \u00e1p trung \u0111i\u1ec3m”.<\/span><\/li>\n<\/ul>\n

    Nguy\u00ean l\u00fd ho\u1ea1t \u0111\u1ed9ng<\/strong><\/span><\/h2>\n

    Ch\u1ebf \u0111\u1ed9 t\u0129nh: Khi t\u00edn hi\u1ec7u v\u00e0o b\u1eb1ng 0.\u00a0<\/span><\/strong><\/p>\n

      \n
    • M\u1ea1ch \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 Q1, Q2 ho\u1ea1t \u0111\u1ed9ng \u1edf ch\u1ebf \u0111\u1ed9 A. Q3, Q4 c\u00f3 th\u1ec3 \u1edf ch\u1ebf \u0111\u1ed9 A ho\u1eb7c AB.\u00a0<\/span><\/li>\n
    • PR1 \u0111\u01b0\u1ee3c \u0111\/ch\u1ec9nh \u0111\u1ec3 Q3, Q4 c\u00f3 \u0111i\u1ec7n \u00e1p ch\u00e2n B b\u1eb1ng nhau, nh\u01b0 v\u1eady \u0111\u1ed9 m\u1edf c\u1ee7a Q3=Q4 v\u00e0 k\u1ebft qu\u1ea3 l\u00e0 \u0111i\u1ec7n \u00e1p t\u1ea1i \u0111i\u1ec3m C b\u1eb1ng 1\/2 \u0111i\u1ec7n \u00e1p ngu\u1ed3n c\u1ea5p (theo s\u01a1 \u0111\u1ed3 m\u1ea1ch \u0111\u01b0\u1ee3c c\u1ea5p 15V th\u00ec \u0111i\u1ec7n \u00e1p \u0111i\u1ec3m C l\u00e0 7.V), \u0111i\u1ec7n \u00e1p t\u1ea1i \u0111i\u1ec3m C g\u1ecdi l\u00e0 “\u0111i\u1ec7n \u00e1p trung \u0111i\u1ec3m”.\u00a0<\/span><\/li>\n
    • T\u1ee5 C5 \u0111\u01b0\u1ee3c n\u1ed1i v\u00e0o \u0111i\u1ec3m C. \u0110i\u1ec7n \u00e1p ban \u0111\u1ea7u tr\u00ean t\u1ee5 ch\u00ednh b\u1eb1ng \u0111i\u1ec7n \u00e1p \u0111i\u1ec3m C (7.5V)<\/span><\/li>\n<\/ul>\n

      Khi t\u00edn hi\u1ec7u v\u00e0o \u1edf b\u00e1n k\u1ef3 d\u01b0\u01a1ng (+):\u00a0<\/span><\/strong><\/p>\n

        \n
      • \u0110i\u1ec7n \u00e1p ch\u00e2n B Q1 t\u0103ng \u2192 Q1 m\u1edf th\u00eam, d\u00f2ng IcQ1 t\u0103ng \u2192 s\u1ee5t \u00e1p tr\u00ean R4 (UR4 = R4xIcQ1) t\u0103ng l\u00e0m cho UcQ1 gi\u1ea3m. \u0110\u1ed9 gi\u1ea3m c\u1ee7a UcQ1 t\u1ef7 l\u1ec7 thu\u1eadn v\u1edbi bi\u00ean \u0111\u1ed9 t\u00edn hi\u1ec7u v\u00e0o.\u00a0<\/span><\/li>\n
      • V\u00ec ch\u00e2n CQ1 n\u1ed1i tr\u1ef1c ti\u1ebfp ch\u00e2n BQ2 n\u00ean khi UcQ1 gi\u1ea3m th\u00ec UbQ2 gi\u1ea3m theo l\u00e0m cho Q2 kh\u00f3a b\u1edbt, nh\u01b0 v\u1eady d\u00f2ng IcQ2 gi\u1ea3m xu\u1ed1ng d\u1eabn \u0111\u1ebfn \u0111i\u1ec7n \u00e1p t\u1ea1i \u0111i\u1ec3m A(UA) v\u00e0 \u0111i\u1ec3m B(UB) \u0111\u1ec1u gi\u1ea3m. – C\u00e1c b\u1ea1n \u0111\u1ec3 \u00fd : Q3 l\u00e0 PNP, Q4 l\u00e0 NPN do v\u1eady khi UA gi\u1ea3m th\u00ec \u0111\u1ed9 m\u1edf Q3 t\u0103ng (m\u1edf th\u00eam), UB gi\u1ea3m th\u00ec \u0111\u1ed9 m\u1edf Q4 gi\u1ea3m (kh\u00f3a b\u1edbt).\u00a0<\/span><\/li>\n
      • V\u00ec Q3 m\u1edf th\u00eam, Q4 kh\u00f3a b\u1edbt l\u00e0m cho \u0111i\u1ec7n \u00e1p t\u1ea1i \u0111i\u1ec3m C t\u0103ng l\u00ean d\u1eabn t\u1edbi t\u1ee5 C5 (ban \u0111\u1ea7u l\u00e0 7.5V) n\u1ea1p, d\u00f2ng n\u1ea1p cho C5 \u0111i t\u1eeb (+) ngu\u1ed3n 15V \u2192 CEQ3 \u2192 R9 \u2192 C5 \u2192 loa \u2192 mass. D\u00f2ng n\u1ea1p qua loa l\u00e0 \u0111i xu\u1ed1ng. \u0110i\u1ec7n \u00e1p tr\u00ean t\u1ee5 C5 l\u00fac n\u00e0y l\u1edbn h\u01a1n 7.5V.<\/span><\/li>\n<\/ul>\n

        Khi t\u00edn hi\u1ec7u v\u00e0o \u1edf b\u00e1n k\u1ef3 \u00e2m (-):<\/span><\/strong><\/p>\n

          \n
        • \u0110i\u1ec7n \u00e1p ch\u00e2n B Q1 gi\u1ea3m \u2192 Q1 kh\u00f3a b\u1edbt, d\u00f2ng IcQ1 gi\u1ea3m \u2192 s\u1ee5t \u00e1p tr\u00ean R4 (UR4 = R4xIcQ1) gi\u1ea3m l\u00e0m cho UcQ1 t\u0103ng. \u0110\u1ed9 t\u0103ng c\u1ee7a UcQ1 t\u1ef7 l\u1ec7 thu\u1eadn v\u1edbi bi\u00ean \u0111\u1ed9 t\u00edn hi\u1ec7u v\u00e0o. – V\u00ec ch\u00e2n CQ1 n\u1ed1i tr\u1ef1c ti\u1ebfp ch\u00e2n BQ2 n\u00ean khi UcQ1 t\u0103ng th\u00ec UbQ2 t\u0103ng theo l\u00e0m cho Q2 m\u1edf th\u00eam, nh\u01b0 v\u1eady d\u00f2ng IcQ2 t\u0103ng l\u00ean d\u1eabn \u0111\u1ebfn \u0111i\u1ec7n \u00e1p t\u1ea1i \u0111i\u1ec3m A(UA) v\u00e0 \u0111i\u1ec3m B(UB) \u0111\u1ec1u t\u0103ng.\u00a0<\/span><\/li>\n
        • C\u00e1c b\u1ea1n \u0111\u1ec3 \u00fd : Q3 l\u00e0 PNP, Q4 l\u00e0 NPN do v\u1eady khi UA t\u0103ng th\u00ec \u0111\u1ed9 m\u1edf Q3 gi\u1ea3m (kh\u00f3a b\u1edbt), UB t\u0103ng th\u00ec \u0111\u1ed9 m\u1edf Q4 t\u0103ng (m\u1edf th\u00eam).\u00a0<\/span><\/li>\n
        • V\u00ec Q3 kh\u00f3a b\u1edbt, Q4 m\u1edf th\u00eam l\u00e0m cho \u0111i\u1ec7n \u00e1p t\u1ea1i \u0111i\u1ec3m C gi\u1ea3m l\u00ean d\u1eabn t\u1edbi t\u1ee5 C5 ph\u00f3ng, d\u00f2ng ph\u00f3ng c\u1ee7a C5 \u0111i t\u1eeb (+) t\u1ee5 \u2192 R10 \u2192 CQ4 \u2192 mass \u2192 loa \u2192 (-)C5. D\u00f2ng ph\u00f3ng qua loa l\u00e0 \u0111i l\u00ean.<\/span><\/li>\n<\/ul>\n

          K\u1ebft lu\u1eadn :<\/strong>\u00a0Nh\u01b0 v\u1eady, v\u1edbi c\u1ea3 chu k\u1ef3 c\u1ee7a t\u00edn hi\u1ec7u v\u00e0o ta thu \u0111\u01b0\u1ee3c 2 d\u00f2ng \u0111i\u1ec7n li\u00ean t\u1ee5c \u0111i xu\u1ed1ng\/\u0111i l\u00ean \u1edf loa, \u0111\u00f3 ch\u00ednh l\u00e0 t\u00edn hi\u1ec7u xoay chi\u1ec1u ra loa. C\u01b0\u1eddng \u0111\u1ed9 2 d\u00f2ng n\u00e0y t\u1ef7 l\u1ec7 thu\u1eadn v\u1edbi bi\u00ean \u0111\u1ed9 t\u00edn hi\u1ec7u xoay chi\u1ec1u v\u00e0o m\u1ea1ch.<\/span><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

          Ph\u00e2n t\u00edch m\u1ea1ch khu\u1ebfch \u0111\u1ea1i \u00e2m thanh c\u01a1 b\u1ea3n d\u00f9ng BJT: T\u1ee5 l\u1ecdc ngu\u1ed3n ch\u00ednh, gi\u00e1 tr\u1ecb c\u1ee7a C6 ph\u1ee5 thu\u1ed9c v\u00e0o d\u00f2ng t\u1ea3i, n\u00f3i c\u00e1ch kh\u00e1c ph\u1ee5 thu\u1ed9c v\u00e0o c\u00f4ng su\u1ea5t ho\u1ea1t \u0111\u1ed9ng c\u1ee7a m\u1ea1ch. N\u1ebfu \u0111i\u1ec7n \u00e1p nu\u00f4i m\u1ea1ch \u0111\u01b0\u1ee3c c\u1ea5p b\u1edfi bi\u1ebfn \u00e1p 50Hz s\u1ebd nghe ti\u1ebfng \u00f9 (nh\u01b0 c\u00f2i t\u1ea7m), n\u1ebfu c\u1ea5p b\u1eb1ng bi\u1ebfn \u00e1p xung t\u1ea7n s\u1ed1 cao s\u1ebd nghe ti\u1ebfng r\u00edt. <\/p>\n","protected":false},"author":95,"featured_media":12094,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[96],"tags":[681],"_links":{"self":[{"href":"https:\/\/hocvienit.vn\/index.php?rest_route=\/wp\/v2\/posts\/1558"}],"collection":[{"href":"https:\/\/hocvienit.vn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hocvienit.vn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hocvienit.vn\/index.php?rest_route=\/wp\/v2\/users\/95"}],"replies":[{"embeddable":true,"href":"https:\/\/hocvienit.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1558"}],"version-history":[{"count":0,"href":"https:\/\/hocvienit.vn\/index.php?rest_route=\/wp\/v2\/posts\/1558\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/hocvienit.vn\/index.php?rest_route=\/wp\/v2\/media\/12094"}],"wp:attachment":[{"href":"https:\/\/hocvienit.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1558"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hocvienit.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1558"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hocvienit.vn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1558"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}